Concourse CI: Use Homebrew 2.2.5 that has sped up brew update

- Homebrew 2.2.5 has improvements that reduce the time that `brew
  update(-reset)` takes from 2 minutes waiting for git to unshallow the
  clone of Homebrew/linuxbrew-core, to 45 seconds:
  Homebrew/brew@243e703

pipeline.yml

@@ -33,7 +33,7 @@ jobs:
             type: docker-image
             source:
               repository: homebrew/brew
-              tag: 2.2.4
+              tag: 2.2.5
           inputs:
             - name: govuk-aws-pr
               path: repo