Delete the Geolocation feature flag.

The Geolocation API implementation was launched a long time ago.

BUG=343592

Review URL: https://codereview.chromium.org/162753006

git-svn-id: svn://svn.chromium.org/blink/trunk@167327 bbb929c8-8fbe-4397-9dbb-9b2b20218538