Bug 801545 - Fix broken json file in test metadata added by previous patch, a=testonly

--HG--
extra : commitid : 3tVCTQyWiEE

dom/imptests/failures/html/dom/test_historical.html.json

@@ -6,5 +6,5 @@
   "Historical DOM features must be removed: getAttributeNode": true,
   "Historical DOM features must be removed: getAttributeNodeNS": true,
   "Historical DOM features must be removed: setAttributeNode": true,
-  "Historical DOM features must be removed: removeAttributeNode": true,
+  "Historical DOM features must be removed: removeAttributeNode": true
 }