Modify the other mnc-dr-arc-* reference

It looks like we are not quite pointing at the R56 Android branch yet, as the
location of the definition has moved (and exists confusingly in two places),
this should correct it for the branch.

BUG=None
TEST=None

Change-Id: Ib62cb8fe50a8eada05519bb31b4020e0a01885cd
Reviewed-on: https://chromium-review.googlesource.com/414617
Commit-Queue: Bernie Thompson <bhthompson@chromium.org>
Tested-by: Bernie Thompson <bhthompson@chromium.org>
Reviewed-by: Junichi Uekawa <uekawa@chromium.org>
diff --git a/lib/constants.py b/lib/constants.py
index a041c37..7697761 100644
--- a/lib/constants.py
+++ b/lib/constants.py
@@ -308,7 +308,7 @@
 INTERNAL_GERRIT_URL = 'https://%s' % INTERNAL_GERRIT_HOST
 
 ANDROID_BUCKET_URL = 'gs://android-build-chromeos/builds'
-ANDROID_BUILD_BRANCH = 'git_mnc-dr-arc-dev'
+ANDROID_BUILD_BRANCH = 'git_mnc-dr-arc-m56'
 ANDROID_BUILD_TARGETS = {
     # TODO(b/29509721): Workaround to roll adb with system image. We want to
     # get rid of this.