Remove code for pickle event queue store.
Remove code for pickle event queue store.

Since we've had the JSON store in all environments for some time, we
no longer need this legacy code.

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