Upgrade GitHub Actions again (#679)

Author: cclauss

.github/workflows/ci.yml

@@ -17,9 +17,9 @@ jobs:
           - "3.9"
           - "3.10"
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install ffmpeg
@@ -37,7 +37,7 @@ jobs:
   black:
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Black
         run: |
           # TODO: use standard `psf/black` action after dropping Python 2 support.