GitHub Actions: Simplify the code to leverage 'tox -e py'

Tracks with https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python#running-tests-with-tox

.github/workflows/tests.yml

@@ -4,18 +4,12 @@ on: [push, pull_request]
 
 jobs:
   tests:
-    name: ${{ matrix.name }}
     runs-on: ${{ matrix.os }}
-
     strategy:
       fail-fast: false
       matrix:
-        include:
-          - { name: "3.12", python: "3.12", os: ubuntu-latest, tox: py312 }
-          - { name: "3.11", python: "3.11", os: ubuntu-latest, tox: py311 }
-          - { name: "3.10", python: "3.10", os: ubuntu-latest, tox: py310 }
-          - { name: "3.9", python: "3.9", os: ubuntu-latest, tox: py39 }
-
+        os: ["ubuntu-latest"]
+        python: ["3.9", "3.10", "3.11", "3.12"]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
@@ -32,9 +26,6 @@ jobs:
         with:
           path: ${{ steps.pip-cache.outputs.dir }}
           key: pip|${{ runner.os }}|${{ matrix.python }}|${{ hashFiles('setup.cfg') }}
-      - name: set full Python version in PY env var
-        # See https://pre-commit.com/#github-actions-example
-        run: echo "PY=$(python -VV | sha256sum | cut -d' ' -f1)" >> $GITHUB_ENV
       - run: pip install tox codecov
       - run: tox -e py