docs: Add community_topic_editing_limit_seconds value to docs.
docs: Add community_topic_editing_limit_seconds value to docs.

This was added to the response in e242ddc. Specifying the value
makes sure that the user does not have to dig in the commit history.

punchagan/zulip,rht/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,punchagan/zulip,hackerkid/zulip,punchagan/zulip,kou/zulip,punchagan/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,showell/zulip,eeshangarg/zulip,showell/zulip,eeshangarg/zulip,showell/zulip,andersk/zulip,eeshangarg/zulip,hackerkid/zulip,punchagan/zulip,kou/zulip,hackerkid/zulip,showell/zulip,eeshangarg/zulip,rht/zulip,showell/zulip,kou/zulip,zulip/zulip,punchagan/zulip,hackerkid/zulip,punchagan/zulip,hackerkid/zulip,showell/zulip,zulip/zulip,andersk/zulip,kou/zulip,kou/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,showell/zulip,andersk/zulip,kou/zulip,andersk/zulip,zulip/zulip,hackerkid/zulip,zulip/zulip,kou/zulip,andersk/zulip,andersk/zulip,rht/zulip