Update GITALY_SERVER_VERSION to 12.9.0
What does this MR do?
Update GITALY_SERVER_VERSION to 12.9.0 due to https://gitlab.com/gitlab-org/release-tools/-/issues/413
Related to https://gitlab.com/gitlab-org/release-tools/-/issues/413
Update GITALY_SERVER_VERSION to 12.9.0 due to https://gitlab.com/gitlab-org/release-tools/-/issues/413
Related to https://gitlab.com/gitlab-org/release-tools/-/issues/413