Fix manifest's externally_connectable to use the correct Hangouts URL

BUG=

Review URL: https://codereview.chromium.org/878413007

Cr-Commit-Position: refs/heads/master@{#314888}

remoting/webapp/crd/manifest.json.jinja2

@@ -62,7 +62,7 @@
 {% endif %}
   "externally_connectable": {
     "matches": [
-        "https://*.talkgadget.google.com/*"
+        "https://*.google.com/hangouts*"
     ]
   },
   "permissions": [