CI: Fix Python 3.11 installation on macOS 13 runners

Once again GitHub Action runners have a minor Python 3 version
preinstalled that we want to upgrade, which will fail because that
versions does not seem to be Homebrew-based.

Enforcing an upgrade will fix the issue as Homebrew can overwrite the
files.

.github/actions/services-validator/action.yaml

@@ -46,7 +46,7 @@ runs:
           eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"
           echo "/home/linuxbrew/.linuxbrew/bin:/home/linuxbrew/.linuxbrew/sbin" >> $GITHUB_PATH
         fi
-        brew install --quiet python3
+        brew install --overwrite --quiet python3
         python3 -m pip install jsonschema json_source_map requests
         echo ::endgroup::