Use wysiwygAdapter instead of global tinyMCE variable

I realised that tinyMCE is already being required as the wysiwygAdapter, so I've updated the code to point to that dependency instead. Still works.

Author: molovo

lib/web/mage/adminhtml/wysiwyg/widget.js

@@ -456,7 +456,7 @@ define([
                     parameters: params,
                     onComplete: function (transport) {
                         try {
-                            editor = tinyMCE.get(this.widgetTargetId);
+                            editor = wysiwyg.get(this.widgetTargetId);
 
                             widgetTools.onAjaxSuccess(transport);
                             widgetTools.dialogWindow.modal('closeModal');
@@ -513,7 +513,7 @@ define([
          * @return {null|wysiwyg.Editor|*}
          */
         getWysiwyg: function () {
-            return tinyMCE.get(this.widgetTargetId);
+            return wysiwyg.get(this.widgetTargetId);
         },
 
         /**