Upgrade to latest versions of github actions.

.github/workflows/index.yml

@@ -9,16 +9,15 @@ jobs:
       matrix:
         python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
         cache: 'pip'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install tox tox-gh-actions
+        python -m pip install tox tox-gh-actions
     - name: Run tests
-      run: |
-        tox
+      run: tox