Run tests in serial, refs #1802

.github/workflows/test.yml

@@ -33,8 +33,7 @@ jobs:
         pip freeze
     - name: Run tests
       run: |
-        pytest -n auto -m "not serial"
-        pytest -m "serial"
+        pytest
     - name: Check if cog needs to be run
       run: |
         cog --check docs/*.rst