ci: Skip python 3.12 for now

The breaking changes begun by the deprecation warnings in 3.10 have
arrived, but according to python/cpython#93453
the scope has changed somewhat (for the better, I think). Don't test
on 3.12 until we've adapted to the new plan.

.github/workflows/test.yml

@@ -44,8 +44,10 @@ jobs:
             tox_env: py310-full
           - python: '3.11'
             tox_env: py311-full
-          - python: '3.12.0-alpha - 3.12'
-            tox_env: py312-full
+          # Need more work for python 3.12. See
+          # https://github.com/python/cpython/issues/93453
+          #- python: '3.12.0-alpha - 3.12'
+          #  tox_env: py312-full
           - python: 'pypy-3.8'
             # Pypy is a lot slower due to jit warmup costs, so don't run the
             # "full" test config there.