Disable Ceph jobs on Python 3.12

These jobs has timed out for a while on all
Python versions and has thus been disabled
so these are now also disabled on Python 3.12

We need to fix these in the future to get
full Ceph coverage.

.github/workflows/gnocchi.yml

@@ -137,6 +137,11 @@ jobs:
             python: py311
           - env: postgresql-ceph
             python: py311
+          # TODO(tobias-urdin): We need to fix below Ceph jobs
+          - env: mysql-ceph
+            python: py312
+          - env: postgresql-ceph
+            python: py312
     steps:
       - uses: actions/checkout@v4
       - run: sudo chown -R 1001:1001 $GITHUB_WORKSPACE