Remove http: scheme from googlefonts links to avoid HTTPS/HTTP mismatches

@juberti please review

Compare the JS console at
https://googlechrome.github.io/webrtc/samples/web/content/getusermedia/
to the JS console for
https://fischman.github.io/webrtc/samples/web/content/getusermedia/

(hint, the former should show a "blocked" message and the font is wrong)