Firstly, change endpoint descriptions in zulip.yaml so that they
match their counterpart in the api docs. Then edit the api docs
so that they use api description markdown extension for displaying
endpoint description.
This makes it a lot more useful for understanding how our flag update
endpoints work.
With significant edits by tabbott to explain what these are.
Fixes#12092.
Since the Zulip API runs on both developement and production
servers, it is misleading to mention "dev servers" when discussing
zuliprc files.
Also, note that it is better to manually edit all of our JS
examples than to implement macro-like functionality that we use
for our Python examples. For our current purposes, it would be
too much work to build a full-blown testing framework for our
JS code examples just so that we can fix a minor wording issue.
Fixes#10672.