Don't show comment button in gutter of diffs on MR discussion tab

app/assets/javascripts/files_comment_button.js

@@ -33,7 +33,7 @@
       this.render = bind(this.render, this);
       this.VIEW_TYPE = $('input#view[type=hidden]').val();
       debounce = _.debounce(this.render, DEBOUNCE_TIMEOUT_DURATION);
-      $(document).off('mouseover', LINE_COLUMN_CLASSES).off('mouseleave', LINE_COLUMN_CLASSES).on('mouseover', LINE_COLUMN_CLASSES, debounce).on('mouseleave', LINE_COLUMN_CLASSES, this.destroy);
+      $(this.filesContainerElement).off('mouseover', LINE_COLUMN_CLASSES).off('mouseleave', LINE_COLUMN_CLASSES).on('mouseover', LINE_COLUMN_CLASSES, debounce).on('mouseleave', LINE_COLUMN_CLASSES, this.destroy);
     }
 
     FilesCommentButton.prototype.render = function(e) {