CI: update action dependencies

Fixes Node 12 deprecation warnings.

- actions/checkout@v2 --> v3
- actions/setup-python@v2 --> v4
- fkirc/skip-duplicate-actions@v3.4.1 --> v5.3.0
  [pinned to hash]

Also set continue-on-error true in skip_duplicate_runs job,
per recommendation in skip-duplicate-actions release notes.

.github/workflows/integration-test.yml

@@ -17,12 +17,13 @@ jobs:
     # Avoid running the live integration tests twice on the same code
     # (to conserve limited sending quotas in the live ESP test accounts)
     runs-on: ubuntu-20.04
+    continue-on-error: true
     outputs:
       should_skip: ${{ steps.skip_check.outputs.should_skip }}
     steps:
       - id: skip_check
-        # uses: fkirc/skip-duplicate-actions@v3.4.1
-        uses: fkirc/skip-duplicate-actions@f75dd6564bb646f95277dc8c3b80612e46a4a1ea
+        # uses: fkirc/skip-duplicate-actions@v5.3.0
+        uses: fkirc/skip-duplicate-actions@12aca0a884f6137d619d6a8a09fcc3406ced5281
         with:
           concurrent_skipping: "same_content_newer"
           cancel_others: "true"
@@ -51,9 +52,9 @@ jobs:
 
     steps:
       - name: Get code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Setup Python ${{ matrix.config.python }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.config.python }}
       - name: Install tox

.github/workflows/release.yml

@@ -23,9 +23,9 @@ jobs:
     environment: release
     steps:
       - name: Get code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Setup Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.10"
 

.github/workflows/test.yml

@@ -19,7 +19,7 @@ jobs:
       envlist: ${{ steps.generate-envlist.outputs.envlist }}
     steps:
       - name: Get code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Install tox-gh-matrix
         run: |
           python -m pip install 'tox<4' 'tox-gh-matrix<0.2'
@@ -47,16 +47,16 @@ jobs:
     timeout-minutes: 15
     steps:
       - name: Get code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Setup Python ${{ matrix.tox.python.version }}
         # Ensure matrix Python version is installed and available for tox
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.tox.python.spec }}
       - name: Setup default Python
         # Change default Python version back to something consistent
         # for installing/running tox
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Install tox