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/snippets/html_elixir.js

@@ -0,0 +1,7 @@
+define("ace/snippets/html_elixir",["require","exports","module"], function(require, exports, module) {
+"use strict";
+
+exports.snippetText =undefined;
+exports.scope = "html_elixir";
+
+});