upgrade: Remove cosmetic-only half of pre-1.4.0 compatibility code.
upgrade: Remove cosmetic-only half of pre-1.4.0 compatibility code.

If we do wind up with a symlink lying around at `local_settings.py`,
it won't do us any harm and shouldn't be materially more confusing
than the regular file we've long had there for almost all installs.
It'll also only last as long as the current deploy.  So just
let it be, and simplify the code a bit.

Also add a line to help the reader understand the remaining half of
this logic (which is essential so long as people might have pre-1.4.0
deploys lying around that they eventually get around to trying to
upgrade).  The fact that it's addressed to a situation which exists
only in the past of this tree, not in its present, makes a brief
comment potentially very helpful.

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