set-typing-status_api: Document `to` as required argument.
set-typing-status_api: Document `to` as required argument.

This was accidentally removed in 27e4f5da92305798b37aa866dfdb480005400d29
as the initial idea was to have another parameter `stream_id`
for stream type messages instead of sending it in this `to` parameter.

Also fixed a description of `to` for `stream` type.

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