Bump actions/setup-python from 3 to 4

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 3 to 4.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](https://github.com/actions/setup-python/compare/v3...v4)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/post-pr.yml

@@ -41,7 +41,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python 3.8
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v4
         with:
           python-version: 3.8
       - uses: actions/cache@v3

.github/workflows/sync-from-external-sources.yml

@@ -13,7 +13,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python 3.8
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v4
         with:
           python-version: 3.8
       - name: Install Prerequisite dependencies
@@ -40,7 +40,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python 3.8
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v4
         with:
           python-version: 3.8
       - name: Install Prerequisite dependencies

.github/workflows/tests.yml

@@ -28,7 +28,7 @@ jobs:
           distribution: 'adopt'
           java-version: '11'
       - uses: gradle/gradle-build-action@v2
-      - uses: actions/setup-python@v3
+      - uses: actions/setup-python@v4
         with:
           python-version: 3.8
       - uses: michaelkaye/setup-matrix-synapse@v1.0.3