bundler: remove deprecated Stop method
bundler: remove deprecated Stop method

All uses under cloud.google.com/go are gone, and there should be
no other uses.

Change-Id: I40e99ecd723b934268473fa06e3f6033b2169dbd
Reviewed-on: https://code-review.googlesource.com/11519
Reviewed-by: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

googleapis/google-api-go-client,googleapis/google-api-go-client,google/google-api-go-client,google/google-api-go-client