chore: 2nd try - simplify python dependencies (#27505)

.github/workflows/superset-python-unittest.yml

@@ -46,27 +46,15 @@ jobs:
         continue-on-error: true
         run: ./scripts/ci_check_no_file_changes.sh python
       - name: Setup Python
+        uses: ./.github/actions/setup-backend/
         if: steps.check.outcome == 'failure'
-        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
-          cache: "pip"
-          cache-dependency-path: "requirements/testing.txt"
-      # TODO: separated requirements.txt file just for unit tests
-      - name: Install dependencies
-        if: steps.check.outcome == 'failure'
-        uses: ./.github/actions/cached-dependencies
-        with:
-          run: |
-            apt-get-install
-            pip-upgrade
-            pip install wheel
-            pip install -r requirements/testing.txt
-            mkdir ${{ github.workspace }}/.temp
       - name: Python unit tests
         if: steps.check.outcome == 'failure'
         env:
           SUPERSET_TESTENV: true
+          SUPERSET_SECRET_KEY: not-a-secret
         run: |
           pytest --durations-min=0.5 --cov-report= --cov=superset ./tests/common ./tests/unit_tests --cache-clear
       - name: Upload code coverage