Actions: correct requirements file name

.github/workflows/tests.yml

@@ -31,7 +31,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+          if [ -f test-requirements.txt ]; then pip install -r test-requirements.txt; fi
       - name: Test with nosetests
         run: |
           nosetests