CI: Update action versions

This hopefully also works around the following issue:

    ...
    Download action repository 'actions/checkout@v2' (SHA:7884fcad6b5d53d10323aee724dc68d8b9096a2e)
    Download action repository 'actions/setup-python@v2' (SHA:7f80679172b057fc5e90d70d197929d454754a5a)
    Error: Can't use 'tar -xzf' extract archive file: /home/runner/work/_actions/_temp_6d6d7f3c-3bc7-4ae4-a142-9ac7d1149883/bde086a4-5d30-4c97-9f99-868525ec3a44.tar.gz. return code: 2.

.github/workflows/gating.yaml

@@ -15,10 +15,10 @@ jobs:
         python-version: ["3.9"]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v3
         with:
           python-version: ${{ matrix.python-version }}
 
@@ -67,10 +67,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Set up Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v3
         with:
           python-version: "3.9"
 
@@ -91,7 +91,7 @@ jobs:
           - Dockerfile
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - uses: hadolint/hadolint-action@v1.5.0
         with:
@@ -114,10 +114,10 @@ jobs:
         python-version: ["3.9"]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v3
         with:
           python-version: ${{ matrix.python-version }}