lang: don't use " " for the default policy text

Firefox (at least) renders it verbatim.

lang/main.json

         "terms": "Terms"
     },
     "startupoverlay": {
-        "policyText": " ",
+        "policyText": " ",
         "title": "__app__ needs to use your microphone and camera."
     },
     "suspendedoverlay": {