ci: update workflows with setup-python to v4.3.0 (#858)

Updates any workflows with setup-python to use v4.3 due to node deprecation warnings.

.github/workflows/docs.yml

@@ -25,9 +25,9 @@ jobs:
         with:
           fetch-depth: 0
 
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v4.3.0
         with:
-          python-version: 3.x
+          python-version: 3.9
 
       - name: Install Python dependencies
         run: pip install -r docs/requirements.txt

.github/workflows/post-release.yml

@@ -35,9 +35,9 @@ jobs:
             exit 1
           fi
 
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v4.3.0
         with:
-          python-version: 3.x
+          python-version: 3.9
 
       - name: Install Python dependencies
         run: pip install -r docs/requirements.txt

.github/workflows/test-docs.yml

@@ -33,9 +33,9 @@ jobs:
         with:
           fetch-depth: 0
 
-      - uses: actions/setup-python@v2
+      - uses: actions/setup-python@v4.3.0
         with:
-          python-version: 3.x
+          python-version: 3.9
 
       - name: Install Python dependencies
         run: pip install -r docs/requirements.txt