base.html: Remove commented-out HTML5 shim code.
base.html: Remove commented-out HTML5 shim code.

From reading the history, I think this was actually never uncommented
in any version of Zulip; and regardless we no longer support IE8.

jrowan/zulip,blaze225/zulip,tommyip/zulip,synicalsyntax/zulip,christi3k/zulip,eeshangarg/zulip,brainwane/zulip,andersk/zulip,susansls/zulip,jrowan/zulip,shubhamdhama/zulip,verma-varsha/zulip,mahim97/zulip,rht/zulip,SmartPeople/zulip,brainwane/zulip,blaze225/zulip,jainayush975/zulip,zulip/zulip,j831/zulip,jainayush975/zulip,vaidap/zulip,kou/zulip,ryanbackman/zulip,verma-varsha/zulip,punchagan/zulip,mahim97/zulip,dhcrzf/zulip,ryanbackman/zulip,verma-varsha/zulip,ryanbackman/zulip,dhcrzf/zulip,JPJPJPOPOP/zulip,punchagan/zulip,andersk/zulip,amanharitsh123/zulip,zulip/zulip,j831/zulip,Galexrt/zulip,jackrzhang/zulip,jainayush975/zulip,hackerkid/zulip,JPJPJPOPOP/zulip,zulip/zulip,kou/zulip,showell/zulip,ryanbackman/zulip,timabbott/zulip,brockwhittaker/zulip,jrowan/zulip,christi3k/zulip,vaidap/zulip,dawran6/zulip,vabs22/zulip,punchagan/zulip,rishig/zulip,aakash-cr7/zulip,shubhamdhama/zulip,christi3k/zulip,vabs22/zulip,rishig/zulip,rht/zulip,vaidap/zulip,shubhamdhama/zulip,brainwane/zulip,hackerkid/zulip,jainayush975/zulip,Galexrt/zulip,souravbadami/zulip,tommyip/zulip,vabs22/zulip,j831/zulip,shubhamdhama/zulip,aakash-cr7/zulip,dhcrzf/zulip,jainayush975/zulip,Galexrt/zulip,timabbott/zulip,JPJPJPOPOP/zulip,j831/zulip,amanharitsh123/zulip,JPJPJPOPOP/zulip,shubhamdhama/zulip,showell/zulip,susansls/zulip,dattatreya303/zulip,tommyip/zulip,jrowan/zulip,mahim97/zulip,christi3k/zulip,susansls/zulip,mahim97/zulip,PhilSk/zulip,blaze225/zulip,j831/zulip,aakash-cr7/zulip,dhcrzf/zulip,brockwhittaker/zulip,showell/zulip,brainwane/zulip,hackerkid/zulip,SmartPeople/zulip,dattatreya303/zulip,jphilipsen05/zulip,Galexrt/zulip,brockwhittaker/zulip,verma-varsha/zulip,synicalsyntax/zulip,synicalsyntax/zulip,verma-varsha/zulip,brockwhittaker/zulip,jphilipsen05/zulip,eeshangarg/zulip,kou/zulip,mahim97/zulip,showell/zulip,showell/zulip,christi3k/zulip,timabbott/zulip,rishig/zulip,jackrzhang/zulip,amanharitsh123/zulip,eeshangarg/zulip,PhilSk/zulip,jainayush975/zulip,jrowan/zulip,Galexrt/zulip,hackerkid/zulip,shubhamdhama/zulip,ryanbackman/zulip,dattatreya303/zulip,JPJPJPOPOP/zulip,tommyip/zulip,souravbadami/zulip,JPJPJPOPOP/zulip,jackrzhang/zulip,zulip/zulip,rht/zulip,mahim97/zulip,punchagan/zulip,jackrzhang/zulip,eeshangarg/zulip,tommyip/zulip,souravbadami/zulip,andersk/zulip,dawran6/zulip,ryanbackman/zulip,susansls/zulip,jphilipsen05/zulip,dawran6/zulip,blaze225/zulip,amanharitsh123/zulip,amanharitsh123/zulip,eeshangarg/zulip,tommyip/zulip,synicalsyntax/zulip,amanharitsh123/zulip,PhilSk/zulip,rishig/zulip,punchagan/zulip,zulip/zulip,jackrzhang/zulip,christi3k/zulip,souravbadami/zulip,zulip/zulip,susansls/zulip,rishig/zulip,tommyip/zulip,SmartPeople/zulip,kou/zulip,hackerkid/zulip,punchagan/zulip,timabbott/zulip,dattatreya303/zulip,jphilipsen05/zulip,brockwhittaker/zulip,andersk/zulip,vabs22/zulip,blaze225/zulip,rht/zulip,PhilSk/zulip,dhcrzf/zulip,synicalsyntax/zulip,timabbott/zulip,vabs22/zulip,eeshangarg/zulip,rishig/zulip,vabs22/zulip,dhcrzf/zulip,PhilSk/zulip,zulip/zulip,shubhamdhama/zulip,Galexrt/zulip,brainwane/zulip,susansls/zulip,aakash-cr7/zulip,vaidap/zulip,souravbadami/zulip,brainwane/zulip,hackerkid/zulip,vaidap/zulip,synicalsyntax/zulip,dhcrzf/zulip,brockwhittaker/zulip,brainwane/zulip,jackrzhang/zulip,kou/zulip,punchagan/zulip,hackerkid/zulip,eeshangarg/zulip,kou/zulip,jphilipsen05/zulip,souravbadami/zulip,SmartPeople/zulip,rht/zulip,timabbott/zulip,Galexrt/zulip,vaidap/zulip,rht/zulip,dawran6/zulip,dattatreya303/zulip,jrowan/zulip,SmartPeople/zulip,PhilSk/zulip,SmartPeople/zulip,jackrzhang/zulip,dawran6/zulip,andersk/zulip,showell/zulip,aakash-cr7/zulip,aakash-cr7/zulip,jphilipsen05/zulip,rishig/zulip,kou/zulip,timabbott/zulip,verma-varsha/zulip,andersk/zulip,andersk/zulip,j831/zulip,dawran6/zulip,rht/zulip,synicalsyntax/zulip,dattatreya303/zulip,showell/zulip,blaze225/zulip