Bug 1253693 - Switch prefer-es6-class React .eslintrc to prefer createClass. r=jlong

MozReview-Commit-ID: 1IuYNShuBwH

--HG--
extra : rebase_source : ced881f0fc5c5949032199ffb61a2ee8892e1f89

devtools/.eslintrc

@@ -40,7 +40,7 @@
     "react/no-did-update-set-state": 1,
     "react/no-direct-mutation-state": 1,
     "react/no-unknown-property": 1,
-    "react/prefer-es6-class": 1,
+    "react/prefer-es6-class": [1, "never"],
     "react/prop-types": 1,
     "react/sort-comp": [1, {
       order: [