Revert "composebox_typeahead: Trigger foucs to send button only after keyup event."
Revert "composebox_typeahead: Trigger foucs to send button only after keyup event."

This reverts commit 3531463ac9c8d100b4cdcd81819eea59487a653c.

I also add a comment explaining why this commit was wrong, that should
help us avoid doing this cleanup again.

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