Only run numpy tests for numpy 1.21

Author: asmeurer

.github/workflows/tests.yml

@@ -30,7 +30,10 @@ jobs:
 
       - name: Run Tests
         run: |
-          pytest
+          if [ "${{ matrix.numpy-version }}" == "1.21" ]; then
+             PYTEST_EXTRA='-k numpy'
+          fi
+          pytest $PYTEST_EXTRA
 
           # Make sure it installs
           python setup.py install