chore(package.json): revert to [email protected] to fix CI builds

The marked npm library brought in a breaking change at 0.2.10.
This commit ensures that we get exactly the version we want.

Closes angular#4822

package.json

@@ -28,7 +28,7 @@
     "karma-sauce-launcher": "~0.1.1",
     "karma-script-launcher": "~0.1.0",
     "yaml-js": "~0.0.8",
-    "marked": "~0.2.9",
+    "marked": "0.2.9",
     "rewire": "1.1.3",
     "grunt-jasmine-node": "~0.1.0",
     "grunt-parallel": "~0.3.1",