Bug 738244 followup followup, remove trailing comma

dom/imptests/failures/html/tests/submission/Opera/microdata/test_001.html.json

@@ -2,6 +2,6 @@
   "document.getItems must return a NodeList": true,
   "itemValue must reflect the src attribute on track elements": true,
   "itemValue must reflect the textContent of time elements with no datetime attribute": true,
-  "itemValue must reflect the datetime attribute of time elements with a datetime attribute": true,
+  "itemValue must reflect the datetime attribute of time elements with a datetime attribute": true
 }