Fix subscription button in notification bot announcements.
Fix subscription button in notification bot announcements.

Fixes #456.

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