Bug 1206670 - Update grunt-html-angular-validate to v0.5.2

It's not yet used in Travis, but we'll hopefully start using it in the
future.

package.json

@@ -19,7 +19,7 @@
   },
   "devDependencies": {
     "grunt-eslint": "16.0.0",
-    "grunt-html-angular-validate": "0.4.1",
+    "grunt-html-angular-validate": "0.5.2",
     "karma": "0.12.37",
     "karma-coverage": "0.5.2",
     "karma-firefox-launcher": "0.1.6",