Off mouse listener from document for diff comment button.

app/assets/javascripts/files_comment_button.js.coffee

@@ -17,6 +17,8 @@ class @FilesCommentButton
     debounce = _.debounce @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, @destroy