Restrict access to branch release-R117 to LTS Refresher group.

BUG=b/566213952

Change-Id: I8c8c45a5542bcdde6cea9570d1c980340e3c4df7
Reviewed-on: https://cos-review.googlesource.com/c/All-Projects/+/212386
Reviewed-by: Derek Taylor <ddtaylor@google.com>
Tested-by: He Gao <hegao@google.com>
Reviewed-by: Miri Amarilio <mirilio@google.com>