Remove state machine code from hotkey.js

With the removal of process_compose_hotkey, the state machine now has only one
state.  Everything else is based on things like "is a text box focused right
now", which is probably a better approach.

(imported from commit 0e39c03956d28e30d2bdbf3b285410ad0cacca3e)

zephyr/static/js/compose.js

@@ -55,7 +55,6 @@ exports.start = function (msg_type, opts) {
         show('private', $("#" + (focus_area || 'private_message_recipient')));
     }
 
-    hotkeys.set_compose();
     is_composing_message = msg_type;
     $(document).trigger($.Event('compose_started.zephyr', opts));
 };