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=sokcevic@google.com

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

git_cache.py

@@ -137,10 +137,6 @@ class Mirror(object):
     u = urlparse.urlparse(self.url)
     if u.netloc == 'chromium.googlesource.com':
       return 'chromium-git-cache'
-    # TODO(tandrii): delete once LUCI migration is completed.
-    # Only public hosts will be supported going forward.
-    elif u.netloc == 'chrome-internal.googlesource.com':
-      return 'chrome-git-cache'
     # Not recognized.
     return None