Zuul encountered deprecated syntax while parsing its configuration for the "manila-grenade-skip-level" job. The "branch" regex didn't conform to RE2 syntax. The "branch" annotation isn't necessary because this repository is branched and zuul is capable of using the job configuration from a specific branch. So we can just drop it instead of fixing it. Change-Id: I12dc07c3a62a7d8ca7b895fd6dc98e165f24e944