ci: Tweak python

.github/workflows/format-backend.yaml

@@ -8,15 +8,19 @@ jobs:
     name: 'Format Backend'
     env:
       PUBLIC_API_BASE_URL: ''
+      RUNNER_TOOL_CACHE: /toolcache
     runs-on: ubuntu-latest
     strategy:
       matrix:
         node-version:
           - latest
+        python-version: [ '2.x', '3.x' ]
     steps:
       - uses: actions/checkout@v4
       - name: Use Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python-version }}
       - name: Use Bun
         uses: oven-sh/setup-bun@v1
       - name: Install dependencies