docs: Remove discussion of old Django templating engine.
docs: Remove discussion of old Django templating engine.

This was unnecessary complexity for users, and in fact, we removed the
code a couple months ago.

vabs22/zulip,tommyip/zulip,rht/zulip,punchagan/zulip,eeshangarg/zulip,mahim97/zulip,showell/zulip,dhcrzf/zulip,verma-varsha/zulip,tommyip/zulip,mahim97/zulip,jrowan/zulip,showell/zulip,brainwane/zulip,dhcrzf/zulip,mahim97/zulip,timabbott/zulip,shubhamdhama/zulip,Galexrt/zulip,dhcrzf/zulip,hackerkid/zulip,vabs22/zulip,brockwhittaker/zulip,andersk/zulip,andersk/zulip,jackrzhang/zulip,rishig/zulip,amanharitsh123/zulip,synicalsyntax/zulip,andersk/zulip,punchagan/zulip,brockwhittaker/zulip,eeshangarg/zulip,brainwane/zulip,verma-varsha/zulip,rht/zulip,mahim97/zulip,zulip/zulip,kou/zulip,showell/zulip,zulip/zulip,kou/zulip,andersk/zulip,brainwane/zulip,synicalsyntax/zulip,jrowan/zulip,mahim97/zulip,hackerkid/zulip,vabs22/zulip,hackerkid/zulip,synicalsyntax/zulip,tommyip/zulip,punchagan/zulip,Galexrt/zulip,synicalsyntax/zulip,eeshangarg/zulip,amanharitsh123/zulip,timabbott/zulip,showell/zulip,vaidap/zulip,showell/zulip,rht/zulip,zulip/zulip,jackrzhang/zulip,kou/zulip,tommyip/zulip,hackerkid/zulip,vabs22/zulip,timabbott/zulip,synicalsyntax/zulip,jackrzhang/zulip,brainwane/zulip,dhcrzf/zulip,kou/zulip,punchagan/zulip,hackerkid/zulip,verma-varsha/zulip,dhcrzf/zulip,brainwane/zulip,punchagan/zulip,brockwhittaker/zulip,eeshangarg/zulip,timabbott/zulip,zulip/zulip,showell/zulip,vabs22/zulip,andersk/zulip,verma-varsha/zulip,vaidap/zulip,Galexrt/zulip,shubhamdhama/zulip,kou/zulip,timabbott/zulip,vaidap/zulip,vaidap/zulip,amanharitsh123/zulip,timabbott/zulip,brockwhittaker/zulip,vaidap/zulip,jrowan/zulip,verma-varsha/zulip,rht/zulip,zulip/zulip,rishig/zulip,punchagan/zulip,rht/zulip,kou/zulip,tommyip/zulip,brainwane/zulip,rht/zulip,rishig/zulip,shubhamdhama/zulip,eeshangarg/zulip,rishig/zulip,synicalsyntax/zulip,jackrzhang/zulip,zulip/zulip,Galexrt/zulip,amanharitsh123/zulip,rishig/zulip,punchagan/zulip,Galexrt/zulip,shubhamdhama/zulip,rishig/zulip,andersk/zulip,hackerkid/zulip,vabs22/zulip,mahim97/zulip,shubhamdhama/zulip,amanharitsh123/zulip,eeshangarg/zulip,jrowan/zulip,shubhamdhama/zulip,brockwhittaker/zulip,verma-varsha/zulip,jackrzhang/zulip,jackrzhang/zulip,vaidap/zulip,tommyip/zulip,zulip/zulip,timabbott/zulip,hackerkid/zulip,showell/zulip,jrowan/zulip,Galexrt/zulip,amanharitsh123/zulip,dhcrzf/zulip,shubhamdhama/zulip,rishig/zulip,dhcrzf/zulip,jackrzhang/zulip,tommyip/zulip,jrowan/zulip,synicalsyntax/zulip,eeshangarg/zulip,andersk/zulip,brockwhittaker/zulip,Galexrt/zulip,kou/zulip,brainwane/zulip,rht/zulip