Remove untested code in is_public_stream().
Remove untested code in is_public_stream().

We were calling valid_stream_name(), but more appropriate
validation checks for stream names happen elsewhere in the codepath.

shubhamdhama/zulip,christi3k/zulip,isht3/zulip,JPJPJPOPOP/zulip,grave-w-grave/zulip,sup95/zulip,timabbott/zulip,verma-varsha/zulip,Diptanshu8/zulip,SmartPeople/zulip,synicalsyntax/zulip,niftynei/zulip,vabs22/zulip,ryanbackman/zulip,ryanbackman/zulip,isht3/zulip,timabbott/zulip,mohsenSy/zulip,shubhamdhama/zulip,jrowan/zulip,arpith/zulip,zulip/zulip,arpith/zulip,punchagan/zulip,timabbott/zulip,susansls/zulip,andersk/zulip,Galexrt/zulip,kou/zulip,vabs22/zulip,Galexrt/zulip,dawran6/zulip,TigorC/zulip,TigorC/zulip,niftynei/zulip,ahmadassaf/zulip,rht/zulip,grave-w-grave/zulip,cosmicAsymmetry/zulip,kou/zulip,blaze225/zulip,jphilipsen05/zulip,grave-w-grave/zulip,dhcrzf/zulip,rishig/zulip,ahmadassaf/zulip,amanharitsh123/zulip,j831/zulip,shubhamdhama/zulip,peguin40/zulip,rishig/zulip,zulip/zulip,joyhchen/zulip,aakash-cr7/zulip,andersk/zulip,sonali0901/zulip,joyhchen/zulip,SmartPeople/zulip,SmartPeople/zulip,Jianchun1/zulip,verma-varsha/zulip,SmartPeople/zulip,rht/zulip,kou/zulip,umkay/zulip,hackerkid/zulip,andersk/zulip,shubhamdhama/zulip,Jianchun1/zulip,dhcrzf/zulip,Diptanshu8/zulip,rishig/zulip,samatdav/zulip,niftynei/zulip,tommyip/zulip,dawran6/zulip,paxapy/zulip,kou/zulip,AZtheAsian/zulip,aakash-cr7/zulip,vikas-parashar/zulip,zacps/zulip,jphilipsen05/zulip,synicalsyntax/zulip,reyha/zulip,eeshangarg/zulip,jackrzhang/zulip,samatdav/zulip,brockwhittaker/zulip,punchagan/zulip,sup95/zulip,aakash-cr7/zulip,vabs22/zulip,showell/zulip,JPJPJPOPOP/zulip,souravbadami/zulip,ahmadassaf/zulip,timabbott/zulip,hackerkid/zulip,paxapy/zulip,punchagan/zulip,tommyip/zulip,reyha/zulip,amanharitsh123/zulip,AZtheAsian/zulip,zacps/zulip,peguin40/zulip,reyha/zulip,sharmaeklavya2/zulip,jphilipsen05/zulip,cosmicAsymmetry/zulip,sharmaeklavya2/zulip,mahim97/zulip,souravbadami/zulip,synicalsyntax/zulip,calvinleenyc/zulip,showell/zulip,vaidap/zulip,synicalsyntax/zulip,sup95/zulip,krtkmj/zulip,mahim97/zulip,isht3/zulip,souravbadami/zulip,joyhchen/zulip,christi3k/zulip,tommyip/zulip,ahmadassaf/zulip,amyliu345/zulip,Juanvulcano/zulip,sonali0901/zulip,vabs22/zulip,mahim97/zulip,rishig/zulip,jphilipsen05/zulip,dhcrzf/zulip,Juanvulcano/zulip,KingxBanana/zulip,showell/zulip,jackrzhang/zulip,hackerkid/zulip,Diptanshu8/zulip,TigorC/zulip,PhilSk/zulip,KingxBanana/zulip,umkay/zulip,j831/zulip,sharmaeklavya2/zulip,dattatreya303/zulip,joyhchen/zulip,arpith/zulip,blaze225/zulip,zulip/zulip,Jianchun1/zulip,sonali0901/zulip,peguin40/zulip,vikas-parashar/zulip,jrowan/zulip,krtkmj/zulip,sup95/zulip,rht/zulip,amanharitsh123/zulip,reyha/zulip,ryanbackman/zulip,hackerkid/zulip,amyliu345/zulip,sharmaeklavya2/zulip,tommyip/zulip,cosmicAsymmetry/zulip,AZtheAsian/zulip,mohsenSy/zulip,susansls/zulip,ahmadassaf/zulip,Jianchun1/zulip,punchagan/zulip,amyliu345/zulip,dattatreya303/zulip,sup95/zulip,SmartPeople/zulip,eeshangarg/zulip,jrowan/zulip,vaidap/zulip,mohsenSy/zulip,paxapy/zulip,rishig/zulip,PhilSk/zulip,arpith/zulip,ahmadassaf/zulip,vikas-parashar/zulip,shubhamdhama/zulip,KingxBanana/zulip,shubhamdhama/zulip,vikas-parashar/zulip,JPJPJPOPOP/zulip,aakash-cr7/zulip,hackerkid/zulip,zulip/zulip,brainwane/zulip,eeshangarg/zulip,Galexrt/zulip,verma-varsha/zulip,dattatreya303/zulip,aakash-cr7/zulip,kou/zulip,christi3k/zulip,ryanbackman/zulip,JPJPJPOPOP/zulip,rishig/zulip,Galexrt/zulip,dhcrzf/zulip,jrowan/zulip,jainayush975/zulip,hackerkid/zulip,dawran6/zulip,krtkmj/zulip,blaze225/zulip,PhilSk/zulip,cosmicAsymmetry/zulip,dattatreya303/zulip,mahim97/zulip,cosmicAsymmetry/zulip,susansls/zulip,zulip/zulip,calvinleenyc/zulip,jainayush975/zulip,showell/zulip,jainayush975/zulip,jackrzhang/zulip,JPJPJPOPOP/zulip,mahim97/zulip,rht/zulip,zacps/zulip,rht/zulip,brockwhittaker/zulip,paxapy/zulip,Juanvulcano/zulip,PhilSk/zulip,vaidap/zulip,Galexrt/zulip,mohsenSy/zulip,peguin40/zulip,vikas-parashar/zulip,brockwhittaker/zulip,punchagan/zulip,timabbott/zulip,paxapy/zulip,isht3/zulip,rht/zulip,eeshangarg/zulip,blaze225/zulip,reyha/zulip,umkay/zulip,synicalsyntax/zulip,tommyip/zulip,synicalsyntax/zulip,PhilSk/zulip,ryanbackman/zulip,dhcrzf/zulip,verma-varsha/zulip,KingxBanana/zulip,jrowan/zulip,grave-w-grave/zulip,showell/zulip,dattatreya303/zulip,krtkmj/zulip,dattatreya303/zulip,amanharitsh123/zulip,j831/zulip,blaze225/zulip,christi3k/zulip,zacps/zulip,jphilipsen05/zulip,Juanvulcano/zulip,Jianchun1/zulip,shubhamdhama/zulip,jphilipsen05/zulip,rht/zulip,christi3k/zulip,rishig/zulip,mohsenSy/zulip,calvinleenyc/zulip,jainayush975/zulip,sup95/zulip,TigorC/zulip,Jianchun1/zulip,brockwhittaker/zulip,samatdav/zulip,sharmaeklavya2/zulip,Diptanshu8/zulip,jackrzhang/zulip,zulip/zulip,tommyip/zulip,blaze225/zulip,j831/zulip,showell/zulip,christi3k/zulip,jackrzhang/zulip,j831/zulip,sonali0901/zulip,ryanbackman/zulip,tommyip/zulip,TigorC/zulip,niftynei/zulip,eeshangarg/zulip,joyhchen/zulip,brainwane/zulip,KingxBanana/zulip,timabbott/zulip,Galexrt/zulip,arpith/zulip,jrowan/zulip,susansls/zulip,zulip/zulip,calvinleenyc/zulip,andersk/zulip,samatdav/zulip,vaidap/zulip,brainwane/zulip,sonali0901/zulip,hackerkid/zulip,vikas-parashar/zulip,verma-varsha/zulip,Galexrt/zulip,calvinleenyc/zulip,brainwane/zulip,vabs22/zulip,zacps/zulip,dawran6/zulip,susansls/zulip,Juanvulcano/zulip,umkay/zulip,susansls/zulip,showell/zulip,Diptanshu8/zulip,kou/zulip,vaidap/zulip,brainwane/zulip,AZtheAsian/zulip,brockwhittaker/zulip,umkay/zulip,andersk/zulip,calvinleenyc/zulip,krtkmj/zulip,niftynei/zulip,grave-w-grave/zulip,dawran6/zulip,kou/zulip,andersk/zulip,brockwhittaker/zulip,mahim97/zulip,dhcrzf/zulip,AZtheAsian/zulip,cosmicAsymmetry/zulip,TigorC/zulip,eeshangarg/zulip,amanharitsh123/zulip,sharmaeklavya2/zulip,KingxBanana/zulip,brainwane/zulip,isht3/zulip,sonali0901/zulip,niftynei/zulip,dawran6/zulip,jackrzhang/zulip,isht3/zulip,amyliu345/zulip,jackrzhang/zulip,SmartPeople/zulip,souravbadami/zulip,brainwane/zulip,dhcrzf/zulip,punchagan/zulip,arpith/zulip,reyha/zulip,andersk/zulip,amyliu345/zulip,j831/zulip,AZtheAsian/zulip,umkay/zulip,PhilSk/zulip,krtkmj/zulip,joyhchen/zulip,jainayush975/zulip,paxapy/zulip,punchagan/zulip,synicalsyntax/zulip,grave-w-grave/zulip,Diptanshu8/zulip,vabs22/zulip,peguin40/zulip,mohsenSy/zulip,umkay/zulip,amanharitsh123/zulip,jainayush975/zulip,verma-varsha/zulip,souravbadami/zulip,ahmadassaf/zulip,samatdav/zulip,souravbadami/zulip,krtkmj/zulip,JPJPJPOPOP/zulip,zacps/zulip,aakash-cr7/zulip,timabbott/zulip,vaidap/zulip,peguin40/zulip,Juanvulcano/zulip,amyliu345/zulip,eeshangarg/zulip,samatdav/zulip