Test older pytest/coverage

.github/workflows/python-package.yml

@@ -75,7 +75,7 @@ jobs:
             - name: Install Python dependencies
               run: |
                 python -m pip install --upgrade pip wheel
-                python -m pip install pytest pytest-cov coveralls
+                python -m pip install pytest\<7 pytest-cov\<4 coveralls
                 python -m pip install git+https://github.com/desihub/desiutil.git@${DESIUTIL_VERSION}#egg=desiutil
                 python -m pip install -r requirements.txt
                 python -m pip install -U 'numpy${{ matrix.numpy-version }}'