CI: update actions major versions to resolve Node 16->20 warning

https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/

.github/workflows/tests-tox.yaml

@@ -31,8 +31,8 @@ jobs:
           - {name: '3.8-MacOS', python: '3.8', os: macos-latest, tox: py38}
           - {name: Typing, python: '3.12', os: ubuntu-latest, tox: typing}
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions/setup-python@v4
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python }}
           cache: 'pip'
@@ -58,7 +58,7 @@ jobs:
           flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
       - name: Cache mypy
         if: matrix.tox == 'typing'
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ./.mypy_cache
           key: mypy|${{ matrix.python }}|${{ hashFiles('pyproject.toml') }}