Update ACE Editor to version 1.2.9

The new ACE editor introduces full support for emojis (and, thereby, UTF-16 characters with high- and low-surrogates). Hence, we can remove our custom fix.

Further, this update will allow emojis to be used in pair programming sessions.

vendor/assets/javascripts/ace/ext-beautify.js

@@ -325,7 +325,7 @@ exports.commands = [{
         exports.beautify(editor.session);
     },
     bindKey: "Ctrl-Shift-B"
-}]
+}];
 
 });
                 (function() {