Upgrade GitHub Actions

.github/workflows/docs.yml

@@ -1,36 +1,36 b''
 name: Build docs
 
 on: [push, pull_request]
 
 jobs:
   build:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Python 3.8
-      uses: actions/setup-python@v2
+    - uses: actions/checkout@v3
+    - name: Set up Python
+      uses: actions/setup-python@v4
       with:
-        python-version: 3.8
+        python-version: 3.x
     - name: Install Graphviz
       run: |
         sudo apt-get update
         sudo apt-get install graphviz
     - name: Install Python dependencies
       run: |
         python -m pip install --upgrade pip setuptools coverage rstvalidator
         pip install -r docs/requirements.txt
     - name: Build docs
       run: |
         python -m rstvalidator long_description.rst
         python tools/fixup_whats_new_pr.py
         make -C docs/ html SPHINXOPTS="-W" \
           PYTHON="coverage run -a" \
           SPHINXBUILD="coverage run -a -m sphinx.cmd.build"
     - name: Generate coverage xml
       run: |
         coverage combine `find . -name .coverage\*` && coverage xml
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v2
       with:
         name: Docs