git-cache: delete support for internal repos.
git-cache: delete support for internal repos.

It worked only because of an all-powerful service account on each bot,
which isn't the case any more.

R=4606aec58cba917397ff2e4738f995e4758694f8@google.com

Change-Id: Id66f9cc44cd416e5b61745c0f690d5a91b3b4c67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2225976
Auto-Submit: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@google.com>
Reviewed-by: Josip Sokcevic <4606aec58cba917397ff2e4738f995e4758694f8@google.com>
Reviewed-by: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Commit-Queue: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools