make sure pip is upgraded

Author: tschaume

.github/workflows/pull-request.yml

@@ -28,7 +28,8 @@ jobs:
           python${{ matrix.python-version }} -m pip install --upgrade pip packaging wheel
           python${{ matrix.python-version }} -m pip install `grep numpy== requirements/ubuntu-latest_py${{ matrix.python-version }}_extras.txt`
           python${{ matrix.python-version }} -m pip install -r requirements/ubuntu-latest_py${{ matrix.python-version }}_extras.txt
-          python${{ matrix.python-version }} -m pip install --no-use-pep517 --no-deps .
+          python${{ matrix.python-version }} -m pip install --upgrade pip
+          python${{ matrix.python-version }} -m pip install --no-deps .
       - name: Test modules
         run: python${{ matrix.python-version }} -m pytest tests
       - name: Test example apps