fix: tests need main requirements installed too

.github/workflows/python-pytest.yml

@@ -22,7 +22,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install flake8 pytest
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         if [ -f tests/requirements.txt ]; then pip install -r tests/requirements.txt; fi
     #    if [ -f pyproject.toml ]; then pip install -r pyproject.toml; fi
     #- name: Lint with flake8