Restrict access to release branch: release-R113 to LTS Refresher group.

BUG=b/475292482

Change-Id: I595d1342e317fc152bfebdbb14ecca97e70e2fa1
Reviewed-on: https://cos-review.googlesource.com/c/All-Projects/+/128955
Reviewed-by: He Gao <hegao@google.com>
Reviewed-by: Chenglong Tang <chenglongtang@google.com>
Tested-by: Kevin Liu <zhihuil@google.com>