Add missing step in GH action

Author: cderici

.github/workflows/test.yaml

@@ -39,6 +39,8 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python }}
+      - name: Install dependencies
+        run: pip install tox
       - name: Run build test target
         run: |
           make build-test