zsh: add /etc/shell caveat
zsh: add /etc/shell caveat

Closes #45683.

Signed-off-by: Dominyk Tiller <53e438f55903875d07efdd98a8aaf887e7208dd3@gmail.com>

decors/homebrew,SteveClement/homebrew,mactkg/homebrew,jab/homebrew,gnawhleinad/homebrew,bukzor/linuxbrew,elgertam/homebrew,slyphon/homebrew,elyscape/homebrew,teslamint/homebrew,moyogo/homebrew,optikfluffel/homebrew,emcrisostomo/homebrew,nelstrom/homebrew,felixonmars/homebrew,apjanke/homebrew,hyuni/homebrew,alebcay/homebrew,manphiz/homebrew,adamliter/homebrew,dutchcoders/homebrew,hyuni/homebrew,slyphon/homebrew,jiashuw/homebrew,alex/homebrew,zhipeng-jia/homebrew,davydden/linuxbrew,Noctem/homebrew,OJFord/homebrew,dgageot/homebrew,afh/homebrew,base10/homebrew,ybott/homebrew,esamson/homebrew,georgschoelly/homebrew,koraktor/homebrew,iandennismiller/homebrew,iandennismiller/homebrew,jmagnusson/homebrew,afh/homebrew,treyharris/homebrew,galaxy001/homebrew,kvs/homebrew,optikfluffel/homebrew,polishgeeks/homebrew,SteveClement/homebrew,dunn/homebrew,ento/homebrew,dericed/homebrew,Cutehacks/homebrew,mkrapp/homebrew,galaxy001/homebrew,dunn/homebrew,mmizutani/homebrew,ge11232002/homebrew,redpen-cc/homebrew,arnested/homebrew,dickeyxxx/homebrew,dongcarl/homebrew,Asuranceturix/homebrew,tschoonj/homebrew,drbenmorgan/linuxbrew,jedahan/homebrew,eighthave/homebrew,joshfriend/homebrew,Chilledheart/homebrew,princeofdarkness76/homebrew,SuperNEMO-DBD/cadfaelbrew,treyharris/homebrew,muellermartin/homebrew,influxdb/homebrew,coldeasy/homebrew,haihappen/homebrew,osimola/homebrew,Habbie/homebrew,dkotvan/homebrew,scorphus/homebrew,reelsense/linuxbrew,drbenmorgan/linuxbrew,sakra/homebrew,afb/homebrew,ablyler/homebrew,zeha/homebrew,vigo/homebrew,kenips/homebrew,TaylorMonacelli/homebrew,Asuranceturix/homebrew,dolfly/homebrew,jamer/homebrew,redpen-cc/homebrew,mobileoverlord/homebrew-1,feelpp/homebrew,moyogo/homebrew,zchee/homebrew,Angeldude/linuxbrew,princeofdarkness76/homebrew,teslamint/homebrew,emcrisostomo/homebrew,gnubila-france/linuxbrew,tjschuck/homebrew,cscetbon/homebrew,ilovezfs/homebrew,miketheman/homebrew,frodeaa/homebrew,scpeters/homebrew,DoomHammer/linuxbrew,tschoonj/homebrew,3van/homebrew,hongkongkiwi/homebrew,coldeasy/homebrew,utzig/homebrew,amjith/homebrew,pdpi/homebrew,osimola/homebrew,jeremiahyan/homebrew,dplarson/homebrew,recruit-tech/homebrew,bigbes/homebrew,influxdata/homebrew,jamer/homebrew,mobileoverlord/homebrew-1,scorphus/homebrew,princeofdarkness76/homebrew,joshua-rutherford/homebrew,felixonmars/homebrew,kad/homebrew,skatsuta/homebrew,Linuxbrew/linuxbrew,getgauge/homebrew,blogabe/homebrew,menivaitsi/homebrew,hanxue/homebrew,TaylorMonacelli/homebrew,coldeasy/homebrew,retrography/homebrew,jiashuw/homebrew,dongcarl/homebrew,ablyler/homebrew,josa42/homebrew,arg/homebrew,iandennismiller/homebrew,amjith/homebrew,bchatard/homebrew,adamliter/homebrew,ear/homebrew,jarrettmeyer/homebrew,ear/homebrew,Noctem/homebrew,alebcay/homebrew,Red54/homebrew,dutchcoders/homebrew,3van/homebrew,SuperNEMO-DBD/cadfaelbrew,hakamadare/homebrew,georgschoelly/homebrew,afb/homebrew,esamson/homebrew,pdpi/homebrew,josa42/homebrew,marcwebbie/homebrew,Asuranceturix/homebrew,gawbul/homebrew,theeternalsw0rd/homebrew,benjaminfrank/homebrew,reelsense/homebrew,feelpp/homebrew,skinny-framework/homebrew,lvicentesanchez/homebrew,elyscape/homebrew,esamson/homebrew,lmontrieux/homebrew,mmizutani/homebrew,esamson/homebrew,cprecioso/homebrew,Habbie/homebrew,frickler01/homebrew,royhodgman/homebrew,sjackman/linuxbrew,tseven/homebrew,dericed/homebrew,miketheman/homebrew,menivaitsi/homebrew,zhipeng-jia/homebrew,michaKFromParis/homebrew-sparks,base10/homebrew,kad/homebrew,vigo/homebrew,royhodgman/homebrew,deorth/homebrew,SteveClement/homebrew,codeout/homebrew,michaKFromParis/homebrew-sparks,LonnyGomes/homebrew,base10/homebrew,sferik/homebrew,reelsense/homebrew,petere/homebrew,hyuni/homebrew,kenips/homebrew,nelstrom/homebrew,megahall/homebrew,Gasol/homebrew,redpen-cc/homebrew,sometimesfood/homebrew,kashif/homebrew,cHoco/homebrew,ento/homebrew,hongkongkiwi/homebrew,Homebrew/homebrew,vigo/homebrew,koraktor/homebrew,dalanmiller/homebrew,DoomHammer/linuxbrew,cHoco/homebrew,LonnyGomes/homebrew,xcezx/homebrew,theeternalsw0rd/homebrew,nandub/homebrew,yazuuchi/homebrew,Chilledheart/homebrew,amjith/homebrew,youtux/homebrew,nelstrom/homebrew,skatsuta/homebrew,brunchboy/homebrew,iostat/homebrew2,marcusandre/homebrew,apjanke/homebrew,miketheman/homebrew,yumitsu/homebrew,cchacin/homebrew,gnubila-france/linuxbrew,ehamberg/homebrew,MoSal/homebrew,ehamberg/homebrew,geoff-codes/homebrew,johanhammar/homebrew,AGWA-forks/homebrew,polishgeeks/homebrew,ExtremeMan/homebrew,gicmo/homebrew,gnubila-france/linuxbrew,ehamberg/homebrew,gnawhleinad/homebrew,afb/homebrew,blogabe/homebrew,frickler01/homebrew,scorphus/homebrew,DoomHammer/linuxbrew,felixonmars/homebrew,jab/homebrew,nelstrom/homebrew,yumitsu/homebrew,muellermartin/homebrew,changzuozhen/homebrew,nandub/homebrew,adamliter/homebrew,jarrettmeyer/homebrew,osimola/homebrew,georgschoelly/homebrew,booi/homebrew,TaylorMonacelli/homebrew,deorth/homebrew,ebouaziz/linuxbrew,slyphon/homebrew,youtux/homebrew,eighthave/homebrew,afh/homebrew,liamstask/homebrew,MartinDelille/homebrew,davydden/linuxbrew,ebouaziz/linuxbrew,hyuni/homebrew,changzuozhen/homebrew,galaxy001/homebrew,ebouaziz/linuxbrew,filcab/homebrew,liamstask/homebrew,reelsense/linuxbrew,SteveClement/homebrew,arnested/homebrew,dunn/homebrew,hanxue/homebrew,Asuranceturix/homebrew,Chilledheart/homebrew,grepnull/homebrew,heinzf/homebrew,kodabb/homebrew,pdxdan/homebrew,josa42/homebrew,joshua-rutherford/homebrew,thinker0/homebrew,influxdb/homebrew,joshua-rutherford/homebrew,liamstask/homebrew,sometimesfood/homebrew,max-horvath/homebrew,utzig/homebrew,ralic/homebrew,bigbes/homebrew,emcrisostomo/homebrew,joshua-rutherford/homebrew,osimola/homebrew,tschoonj/homebrew,booi/homebrew,jmagnusson/homebrew,manphiz/homebrew,quantumsteve/homebrew,SteveClement/homebrew,scpeters/homebrew,dalanmiller/homebrew,a-b/homebrew,keith/homebrew,recruit-tech/homebrew,hongkongkiwi/homebrew,base10/homebrew,Cutehacks/homebrew,influxdb/homebrew,jab/homebrew,lvicentesanchez/linuxbrew,OJFord/homebrew,polishgeeks/homebrew,knpwrs/homebrew,MoSal/homebrew,Homebrew/homebrew,iostat/homebrew2,frodeaa/homebrew,cosmo0920/homebrew,Red54/homebrew,totalvoidness/homebrew,michaKFromParis/homebrew-sparks,kevinastone/homebrew,lvicentesanchez/linuxbrew,heinzf/homebrew,gnawhleinad/homebrew,tsaeger/homebrew,decors/homebrew,alex/homebrew,petere/homebrew,youtux/homebrew,grepnull/homebrew,cprecioso/homebrew,pdpi/homebrew,xcezx/homebrew,lvicentesanchez/homebrew,johanhammar/homebrew,pdxdan/homebrew,danieroux/homebrew,bchatard/homebrew,gvangool/homebrew,LinusU/homebrew,lmontrieux/homebrew,arg/homebrew,megahall/homebrew,pdxdan/homebrew,nandub/homebrew,lvicentesanchez/homebrew,Gasol/homebrew,3van/homebrew,danabrand/linuxbrew,optikfluffel/homebrew,sometimesfood/homebrew,pcottle/homebrew,jiashuw/homebrew,BrewTestBot/homebrew,Angeldude/linuxbrew,xcezx/homebrew,Homebrew/homebrew,Homebrew/homebrew,tstack/homebrew,scpeters/homebrew,vihangm/homebrew,sometimesfood/homebrew,MartinDelille/homebrew,kashif/homebrew,johanhammar/homebrew,arg/homebrew,pcottle/homebrew,haihappen/homebrew,danabrand/linuxbrew,tstack/homebrew,dutchcoders/homebrew,xyproto/homebrew,danabrand/linuxbrew,polishgeeks/homebrew,marcusandre/homebrew,lrascao/homebrew,kashif/homebrew,xcezx/homebrew,lrascao/homebrew,gawbul/homebrew,AGWA-forks/homebrew,haihappen/homebrew,royhodgman/homebrew,OJFord/homebrew,yumitsu/homebrew,okuramasafumi/homebrew,cHoco/homebrew,kenips/homebrew,frickler01/homebrew,Red54/homebrew,feelpp/homebrew,bchatard/homebrew,dplarson/homebrew,pcottle/homebrew,Homebrew/linuxbrew,retrography/homebrew,skinny-framework/homebrew,jconley/homebrew,jamer/homebrew,frickler01/homebrew,ge11232002/homebrew,gawbul/homebrew,zchee/homebrew,drbenmorgan/linuxbrew,knpwrs/homebrew,koraktor/homebrew,decors/homebrew,Cutehacks/homebrew,jsjohnst/homebrew,codeout/homebrew,blogabe/homebrew,tutumcloud/homebrew,jedahan/homebrew,ybott/homebrew,arnested/homebrew,hakamadare/homebrew,tstack/homebrew,gicmo/homebrew,skinny-framework/homebrew,sjackman/linuxbrew,ear/homebrew,TaylorMonacelli/homebrew,slyphon/homebrew,galaxy001/homebrew,Asuranceturix/homebrew,dgageot/homebrew,benjaminfrank/homebrew,danieroux/homebrew,alex/homebrew,princeofdarkness76/homebrew,Noctem/homebrew,keith/homebrew,reelsense/homebrew,tutumcloud/homebrew,scpeters/homebrew,tseven/homebrew,frodeaa/homebrew,felixonmars/homebrew,codeout/homebrew,tjschuck/homebrew,jsjohnst/homebrew,influxdata/homebrew,ryanfb/homebrew,jmagnusson/homebrew,mactkg/homebrew,megahall/homebrew,tsaeger/homebrew,SuperNEMO-DBD/cadfaelbrew,drewwells/homebrew,zeha/homebrew,saketkc/linuxbrew,dplarson/homebrew,iostat/homebrew2,reelsense/linuxbrew,xyproto/homebrew,arnested/homebrew,elyscape/homebrew,tutumcloud/homebrew,davydden/linuxbrew,ralic/homebrew,joshfriend/homebrew,pcottle/homebrew,Linuxbrew/linuxbrew,vihangm/homebrew,ExtremeMan/homebrew,youtux/homebrew,ralic/homebrew,eighthave/homebrew,yangj1e/homebrew,dalanmiller/homebrew,kevinastone/homebrew,quantumsteve/homebrew,mobileoverlord/homebrew-1,thinker0/homebrew,drbenmorgan/linuxbrew,Gasol/homebrew,AlexejK/homebrew,cosmo0920/homebrew,chadcatlett/homebrew,decors/homebrew,LinusU/homebrew,ryanfb/homebrew,zhipeng-jia/homebrew,yangj1e/homebrew,hanxue/homebrew,zeha/homebrew,brunchboy/homebrew,deorth/homebrew,razamatan/homebrew,cchacin/homebrew,muellermartin/homebrew,brunchboy/homebrew,amjith/homebrew,feelpp/homebrew,Habbie/homebrew,kodabb/homebrew,scorphus/homebrew,hakamadare/homebrew,MoSal/homebrew,ybott/homebrew,dickeyxxx/homebrew,marcusandre/homebrew,jconley/homebrew,vihangm/homebrew,ento/homebrew,moyogo/homebrew,ExtremeMan/homebrew,ilovezfs/homebrew,cosmo0920/homebrew,hakamadare/homebrew,recruit-tech/homebrew,muellermartin/homebrew,menivaitsi/homebrew,dolfly/homebrew,LonnyGomes/homebrew,Homebrew/linuxbrew,utzig/homebrew,patrickmckenna/homebrew,dolfly/homebrew,influxdb/homebrew,nandub/homebrew,sakra/homebrew,dalanmiller/homebrew,apjanke/homebrew,razamatan/homebrew,mobileoverlord/homebrew-1,Habbie/homebrew,lvicentesanchez/homebrew,dunn/homebrew,johanhammar/homebrew,jsjohnst/homebrew,ablyler/homebrew,teslamint/homebrew,tutumcloud/homebrew,pcottle/homebrew,LinusU/homebrew,utzig/homebrew,AlexejK/homebrew,dkotvan/homebrew,miketheman/homebrew,ebouaziz/linuxbrew,dickeyxxx/homebrew,cchacin/homebrew,tjschuck/homebrew,koraktor/homebrew,Noctem/homebrew,keith/homebrew,apjanke/homebrew,geoff-codes/homebrew,Homebrew/linuxbrew,mkrapp/homebrew,mactkg/homebrew,heinzf/homebrew,cscetbon/homebrew,pdxdan/homebrew,adamliter/homebrew,davidcelis/homebrew,petere/homebrew,zchee/homebrew,megahall/homebrew,blogabe/homebrew,alebcay/homebrew,geoff-codes/homebrew,drewwells/homebrew,bukzor/linuxbrew,kad/homebrew,ryanfb/homebrew,treyharris/homebrew,booi/homebrew,retrography/homebrew,optikfluffel/homebrew,elgertam/homebrew,reelsense/linuxbrew,skinny-framework/homebrew,dutchcoders/homebrew,heinzf/homebrew,cchacin/homebrew,sjackman/linuxbrew,chadcatlett/homebrew,ge11232002/homebrew,theeternalsw0rd/homebrew,getgauge/homebrew,max-horvath/homebrew,xyproto/homebrew,grepnull/homebrew,MoSal/homebrew,changzuozhen/homebrew,patrickmckenna/homebrew,jarrettmeyer/homebrew,kvs/homebrew,bukzor/linuxbrew,getgauge/homebrew,tsaeger/homebrew,davidcelis/homebrew,royhodgman/homebrew,razamatan/homebrew,AlexejK/homebrew,gnawhleinad/homebrew,tsaeger/homebrew,liamstask/homebrew,yazuuchi/homebrew,gvangool/homebrew,hanxue/homebrew,Linuxbrew/linuxbrew,jarrettmeyer/homebrew,haihappen/homebrew,manphiz/homebrew,manphiz/homebrew,zeha/homebrew,lmontrieux/homebrew,kashif/homebrew,a-b/homebrew,moyogo/homebrew,lvicentesanchez/linuxbrew,jiashuw/homebrew,tschoonj/homebrew,gvangool/homebrew,sferik/homebrew,gicmo/homebrew,georgschoelly/homebrew,tstack/homebrew,arg/homebrew,SuperNEMO-DBD/cadfaelbrew,afb/homebrew,ento/homebrew,sferik/homebrew,dgageot/homebrew,patrickmckenna/homebrew,jab/homebrew,kenips/homebrew,quantumsteve/homebrew,bchatard/homebrew,getgauge/homebrew,dickeyxxx/homebrew,thinker0/homebrew,emcrisostomo/homebrew,pdpi/homebrew,marcwebbie/homebrew,jconley/homebrew,Homebrew/linuxbrew,filcab/homebrew,elyscape/homebrew,xyproto/homebrew,danabrand/linuxbrew,cprecioso/homebrew,ybott/homebrew,influxdata/homebrew,totalvoidness/homebrew,jmagnusson/homebrew,3van/homebrew,recruit-tech/homebrew,ryanfb/homebrew,kodabb/homebrew,dericed/homebrew,mkrapp/homebrew,filcab/homebrew,kodabb/homebrew,kevinastone/homebrew,ralic/homebrew,grepnull/homebrew,petere/homebrew,okuramasafumi/homebrew,ilovezfs/homebrew,elgertam/homebrew,redpen-cc/homebrew,danieroux/homebrew,sjackman/linuxbrew,tseven/homebrew,Linuxbrew/linuxbrew,BrewTestBot/homebrew,tjschuck/homebrew,BrewTestBot/homebrew,hongkongkiwi/homebrew,a-b/homebrew,yazuuchi/homebrew,knpwrs/homebrew,changzuozhen/homebrew,dplarson/homebrew,keith/homebrew,lrascao/homebrew,coldeasy/homebrew,danieroux/homebrew,sferik/homebrew,zhipeng-jia/homebrew,cprecioso/homebrew,benjaminfrank/homebrew,vigo/homebrew,kvs/homebrew,iandennismiller/homebrew,dericed/homebrew,Gasol/homebrew,benjaminfrank/homebrew,davidcelis/homebrew,AGWA-forks/homebrew,okuramasafumi/homebrew,MartinDelille/homebrew,AGWA-forks/homebrew,ablyler/homebrew,razamatan/homebrew,alebcay/homebrew,reelsense/homebrew,jconley/homebrew,totalvoidness/homebrew,sakra/homebrew,kad/homebrew,bigbes/homebrew,LonnyGomes/homebrew,a-b/homebrew,menivaitsi/homebrew,cosmo0920/homebrew,Cutehacks/homebrew,gvangool/homebrew,frodeaa/homebrew,filcab/homebrew,jeremiahyan/homebrew,skatsuta/homebrew,dkotvan/homebrew,iostat/homebrew2,theeternalsw0rd/homebrew,afh/homebrew,ehamberg/homebrew,marcwebbie/homebrew,joshfriend/homebrew,Angeldude/linuxbrew,skatsuta/homebrew,kvs/homebrew,dongcarl/homebrew,ExtremeMan/homebrew,Angeldude/linuxbrew,influxdata/homebrew,lmontrieux/homebrew,patrickmckenna/homebrew,cHoco/homebrew,drewwells/homebrew,jamer/homebrew,ilovezfs/homebrew,eighthave/homebrew,BrewTestBot/homebrew,yangj1e/homebrew,bigbes/homebrew,gicmo/homebrew,saketkc/linuxbrew,mmizutani/homebrew,LinusU/homebrew,brunchboy/homebrew,marcwebbie/homebrew,gnubila-france/linuxbrew,DoomHammer/linuxbrew,geoff-codes/homebrew,jedahan/homebrew,lvicentesanchez/linuxbrew,max-horvath/homebrew,Chilledheart/homebrew,saketkc/linuxbrew,dkotvan/homebrew,dgageot/homebrew,AlexejK/homebrew,MartinDelille/homebrew,zchee/homebrew,drewwells/homebrew,chadcatlett/homebrew,mactkg/homebrew,kevinastone/homebrew,teslamint/homebrew,ge11232002/homebrew,ear/homebrew,jsjohnst/homebrew,codeout/homebrew,davidcelis/homebrew,mmizutani/homebrew,bukzor/linuxbrew,jedahan/homebrew,elgertam/homebrew,vihangm/homebrew,OJFord/homebrew,Red54/homebrew,dolfly/homebrew,treyharris/homebrew,marcusandre/homebrew,tseven/homebrew,jeremiahyan/homebrew,jeremiahyan/homebrew,max-horvath/homebrew,alex/homebrew,saketkc/linuxbrew,cscetbon/homebrew,yazuuchi/homebrew,knpwrs/homebrew,dongcarl/homebrew,retrography/homebrew,davydden/linuxbrew,quantumsteve/homebrew,yangj1e/homebrew,okuramasafumi/homebrew,thinker0/homebrew,sakra/homebrew,totalvoidness/homebrew