Used Python 3.10 for docs and linters GitHub actions.

.github/workflows/docs.yml

@@ -21,7 +21,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: 3.9
+          python-version: '3.10'
       - name: Cache dependencies
         uses: actions/cache@v2
         with:

.github/workflows/linters.yml

@@ -20,7 +20,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: 3.9
+          python-version: '3.10'
       - run: python -m pip install flake8
       - name: flake8
         uses: liskin/gh-problem-matcher-wrap@v1
@@ -36,7 +36,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: 3.9
+          python-version: '3.10'
       - run: python -m pip install isort
       - name: isort
         uses: liskin/gh-problem-matcher-wrap@v1