Revert "Restrict access to branch release-R121 to LTS Refresher group."

This reverts commit 78570cb25909a10c72ecd94fa1aa554356fb79a9.

Reason for revert: merge is done

Change-Id: I268399ca79d90e61f463502555eba02973ab8c21
Reviewed-on: https://cos-review.googlesource.com/c/All-Projects/+/212587
Reviewed-by: Derek Taylor <ddtaylor@google.com>
Tested-by: He Gao <hegao@google.com>