message edit: Fix `stream_id` description in API docs.
message edit: Fix `stream_id` description in API docs.

Since caa08d76b53c06ba716c00d9b992556065c11a34, we no longer have
a common component for stream IDs in zulip.yaml, so we might as
well change the description to be specific and clear.

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