`@phlexbot format` has problems when multiple actions need to commit changes

If more than one workflow triggered by `@phlexbot format` needs to commit and push changes, then only the first one wins with the others failing due to non-fast-forward push. We should either remove `@phlexbot format` in favor of per-workflow directives, or (more robust) implement a bounded rebase/retry loop on failed commit for all "fix" workflows.