Remove never reached area in GeoNotifier

Allowance checking in the runSuccessCallback is useless and annoying.
It is already checked right before calling.

BUG=387656

Review URL: https://codereview.chromium.org/402483003

git-svn-id: svn://svn.chromium.org/blink/trunk@178317 bbb929c8-8fbe-4397-9dbb-9b2b20218538