hotkey: Clear message sent success banners too on escape keypress.

Without this, if there was a success compose banner and user pressed
escape key, no banners were hidden and the same behaviour was repeated
without compose ever closing.

web/src/hotkey.js

@@ -310,6 +310,7 @@ export function process_escape_key(e) {
 
             // Check for errors in compose box; close errors if they exist
             if ($(".compose_banner").length) {
+                compose_banner.clear_message_sent_banners();
                 compose_banner.clear_errors();
                 compose_banner.clear_warnings();
                 return true;