unpinned dependencies in CI

.github/workflows/python-package.yml

@@ -39,7 +39,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        python -m pip install --requirement requirements.txt
+        python -m pip install --requirement requirements.in
         python -m pip install .
     - name: Test with pytest
       run: |