api docs: Sync list of realm settings with reality.
api docs: Sync list of realm settings with reality.

It turns out these were just wrong.  We fix a few things:
* Sort the list of settings so that it's possible to compare with reality.
* Deleted additional fields that don't actually exist.
* Fixed various fields missing past feature level updates.

andersk/zulip,zulip/zulip,kou/zulip,zulip/zulip,rht/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,kou/zulip,andersk/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,kou/zulip,rht/zulip,rht/zulip,kou/zulip,zulip/zulip,kou/zulip,andersk/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,andersk/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,eeshangarg/zulip