[ci] python version is now mandatory for gh python setup

.github/workflows/linter.yml

@@ -12,6 +12,8 @@ jobs:
     - uses: actions/checkout@v3
     - name: Set up Python
       uses: actions/setup-python@v4
+      with:
+        python-version: "3.9"
     - name: Install dependencies
       run: pip install -r requirements-ci.txt
     - name: Run flake8 linter

.github/workflows/process_linter_results.yml

@@ -37,6 +37,8 @@ jobs:
       - run: unzip linter_output.zip
       - name: Set up Python
         uses: actions/setup-python@v4
+        with:
+          python-version: "3.8"
       # pinned to lintly 0.5.0 due to https://github.com/grantmcconnaughey/Lintly/issues/41
       - name: Install dependencies
         run: pip install lintly==0.5.0 markupsafe==2.0.1