When a repository doesn't work with Gerrit, it doesn't make sense to
create GerritAccessor and pass it to presubmit checks.
gerrit.host is stored into git config when codereview.settings file contains GERRIT_HOST item.

Change-Id: I9740950caf85a1da9a6e4ae12e3612625cf0cec5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3687235Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Auto-Submit: Aleksey Khoroshilov <akhoroshilov@brave.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>