fix import

Author: Joseph Hamman

.github/workflows/pypipublish.yaml

@@ -66,7 +66,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           python -m pip install dist/xarray_schema*.whl
-          python -c "import xarray-schema; print(xarray-schema.__version__)"
+          python -c "import xarray_schema; print(xarray_schema.__version__)"
 
   upload-to-pypi:
     needs: test-built-dist