Remove geolocationDestroyed() client notification.

This WebGeolocationClient notification is no longer issued by Blink
to the embedder (Blink r180944), nor implemented (Chromium r292890.)

R=
BUG=

Review URL: https://codereview.chromium.org/521223003

git-svn-id: svn://svn.chromium.org/blink/trunk@181206 bbb929c8-8fbe-4397-9dbb-9b2b20218538