Drop custom GHA

.github/workflows/tests.yml

@@ -31,17 +31,3 @@ jobs:
         run: |
           ENV_PREFIX=$(tr -C -d "0-9" <<< "${{ matrix.python-version }}")
           TOXENV=$(tox --listenvs | grep "^py$ENV_PREFIX" | tr '\n' ',') python -m tox
-
-  lint:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - name: Set up Python
-        uses: actions/setup-python@v2
-        with:
-          python-version: 3.9
-      - name: Install dependencies
-        run: |
-          python -m pip install --upgrade pip tox
-      - name: Run lint
-        run: tox -e qa