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/mode-lucene.js

@@ -57,6 +57,7 @@ var LuceneHighlightRules = require("./lucene_highlight_rules").LuceneHighlightRu
 
 var Mode = function() {
     this.HighlightRules = LuceneHighlightRules;
+    this.$behaviour = this.$defaultBehaviour;
 };
 
 oop.inherits(Mode, TextMode);