Add colefaust@ to OWNERS

I do a lot of errorprone maintenance and it's helpful to be an
OWNER of the errorprone plugins so I can update them along with
errorprone.

Also remove jsharkey, as he has left google.

Bug: 253827323
Test: Presubmits
Change-Id: I271063caf589bca715b586c8da48468efdfa03d8