message_scroll: Remove misleading comment.
message_scroll: Remove misleading comment.

The hacky code referenced in this comment was removed in
d59ccd4c0f386b91b03003e9a2aca972254a10f4.

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