add note about fixing old migrations that break on the expired column
add note about fixing old migrations that break on the expired column

gogobook/wagtail,darith27/wagtail,darith27/wagtail,Toshakins/wagtail,davecranwell/wagtail,davecranwell/wagtail,chrxr/wagtail,rv816/wagtail,benjaoming/wagtail,mephizzle/wagtail,marctc/wagtail,torchbox/wagtail,bjesus/wagtail,hamsterbacke23/wagtail,quru/wagtail,Tivix/wagtail,stevenewey/wagtail,janusnic/wagtail,mikedingjan/wagtail,thenewguy/wagtail,Klaudit/wagtail,inonit/wagtail,stevenewey/wagtail,torchbox/wagtail,Tivix/wagtail,nealtodd/wagtail,mephizzle/wagtail,JoshBarr/wagtail,kurtrwall/wagtail,JoshBarr/wagtail,rsalmaso/wagtail,takeshineshiro/wagtail,hamsterbacke23/wagtail,100Shapes/wagtail,FlipperPA/wagtail,KimGlazebrook/wagtail-experiment,nrsimha/wagtail,nrsimha/wagtail,taedori81/wagtail,nimasmi/wagtail,chrxr/wagtail,mayapurmedia/wagtail,nealtodd/wagtail,kaedroho/wagtail,willcodefortea/wagtail,kaedroho/wagtail,torchbox/wagtail,benemery/wagtail,jordij/wagtail,mikedingjan/wagtail,chimeno/wagtail,nutztherookie/wagtail,nutztherookie/wagtail,kurtrwall/wagtail,takeshineshiro/wagtail,dresiu/wagtail,iho/wagtail,nilnvoid/wagtail,dresiu/wagtail,Tivix/wagtail,darith27/wagtail,jnns/wagtail,gasman/wagtail,serzans/wagtail,jorge-marques/wagtail,thenewguy/wagtail,iansprice/wagtail,nealtodd/wagtail,hamsterbacke23/wagtail,FlipperPA/wagtail,dresiu/wagtail,davecranwell/wagtail,willcodefortea/wagtail,quru/wagtail,hanpama/wagtail,takeflight/wagtail,mayapurmedia/wagtail,thenewguy/wagtail,willcodefortea/wagtail,inonit/wagtail,wagtail/wagtail,rv816/wagtail,bjesus/wagtail,benjaoming/wagtail,stevenewey/wagtail,bjesus/wagtail,WQuanfeng/wagtail,tangentlabs/wagtail,zerolab/wagtail,kurtw/wagtail,taedori81/wagtail,zerolab/wagtail,serzans/wagtail,hanpama/wagtail,torchbox/wagtail,JoshBarr/wagtail,takeshineshiro/wagtail,benjaoming/wagtail,bjesus/wagtail,takeflight/wagtail,iho/wagtail,jnns/wagtail,100Shapes/wagtail,gasman/wagtail,kurtw/wagtail,nimasmi/wagtail,mixxorz/wagtail,nilnvoid/wagtail,rjsproxy/wagtail,chimeno/wagtail,nilnvoid/wagtail,FlipperPA/wagtail,rsalmaso/wagtail,kaedroho/wagtail,thenewguy/wagtail,iansprice/wagtail,serzans/wagtail,stevenewey/wagtail,benjaoming/wagtail,m-sanders/wagtail,chimeno/wagtail,kaedroho/wagtail,janusnic/wagtail,takeshineshiro/wagtail,rv816/wagtail,serzans/wagtail,mixxorz/wagtail,hamsterbacke23/wagtail,mephizzle/wagtail,kaedroho/wagtail,iansprice/wagtail,jorge-marques/wagtail,jnns/wagtail,jordij/wagtail,nutztherookie/wagtail,zerolab/wagtail,KimGlazebrook/wagtail-experiment,marctc/wagtail,timorieber/wagtail,chrxr/wagtail,timorieber/wagtail,Toshakins/wagtail,mikedingjan/wagtail,KimGlazebrook/wagtail-experiment,tangentlabs/wagtail,mjec/wagtail,darith27/wagtail,wagtail/wagtail,marctc/wagtail,Klaudit/wagtail,rjsproxy/wagtail,benemery/wagtail,WQuanfeng/wagtail,kurtw/wagtail,chimeno/wagtail,nimasmi/wagtail,Toshakins/wagtail,willcodefortea/wagtail,mikedingjan/wagtail,kurtw/wagtail,mixxorz/wagtail,nilnvoid/wagtail,wagtail/wagtail,Klaudit/wagtail,janusnic/wagtail,takeflight/wagtail,Klaudit/wagtail,gogobook/wagtail,mjec/wagtail,wagtail/wagtail,inonit/wagtail,m-sanders/wagtail,takeflight/wagtail,kurtrwall/wagtail,iho/wagtail,WQuanfeng/wagtail,nealtodd/wagtail,marctc/wagtail,m-sanders/wagtail,nrsimha/wagtail,quru/wagtail,mayapurmedia/wagtail,zerolab/wagtail,chimeno/wagtail,zerolab/wagtail,gasman/wagtail,nimasmi/wagtail,quru/wagtail,JoshBarr/wagtail,mayapurmedia/wagtail,jorge-marques/wagtail,timorieber/wagtail,taedori81/wagtail,nutztherookie/wagtail,rsalmaso/wagtail,jorge-marques/wagtail,Pennebaker/wagtail,tangentlabs/wagtail,100Shapes/wagtail,Tivix/wagtail,kurtrwall/wagtail,timorieber/wagtail,mixxorz/wagtail,rjsproxy/wagtail,mephizzle/wagtail,mjec/wagtail,mjec/wagtail,gogobook/wagtail,davecranwell/wagtail,taedori81/wagtail,jordij/wagtail,WQuanfeng/wagtail,hanpama/wagtail,chrxr/wagtail,jnns/wagtail,janusnic/wagtail,rsalmaso/wagtail,taedori81/wagtail,inonit/wagtail,Toshakins/wagtail,thenewguy/wagtail,dresiu/wagtail,gasman/wagtail,benemery/wagtail,mixxorz/wagtail,hanpama/wagtail,Pennebaker/wagtail,iansprice/wagtail,FlipperPA/wagtail,iho/wagtail,jordij/wagtail,Pennebaker/wagtail,rjsproxy/wagtail,tangentlabs/wagtail,m-sanders/wagtail,Pennebaker/wagtail,gasman/wagtail,dresiu/wagtail,rsalmaso/wagtail,KimGlazebrook/wagtail-experiment,jorge-marques/wagtail,wagtail/wagtail,nrsimha/wagtail,rv816/wagtail,benemery/wagtail,gogobook/wagtail