fix: retrieve raw content from TinyMCE editor (#31212)

During the upgrade to TinyMCE v5, we changed the content format to `text`.
However, it ignores changes in HTML tags. This reverts the format to `raw`.

xmodule/js/src/html/edit.js

@@ -1390,7 +1390,7 @@
       haven't dirtied the Editor. Store the raw content so we can compare it later.
        */
       this.starting_content = visualEditor.getContent({
-        format: "text",
+        format: "raw",
         no_events: 1
       });
       return visualEditor.focus();
@@ -1410,7 +1410,7 @@
       if (this.editor_choice === 'visual') {
         visualEditor = this.getVisualEditor();
         raw_content = visualEditor.getContent({
-          format: "text",
+          format: "raw",
           no_events: 1
         });
         if (this.starting_content !== raw_content) {