ci: Update GitHub Actions

https://github.com/actions/checkout
https://github.com/actions/setup-python

.github/workflows/ci.yaml

@@ -14,9 +14,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Set up Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
       - run:
           python -m pip install flake8 flake8-import-order doc8 sphinx
             rstcheck[sphinx]
@@ -41,9 +41,9 @@ jobs:
           - '3.10'
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Append GitHub Actions system path