Revert "Try running every test at once, refs #1955"

This reverts commit 51ee8caa4a.

.github/workflows/test.yml

@@ -33,9 +33,8 @@ jobs:
         pip freeze
     - name: Run tests
       run: |
-        # pytest -n auto -m "not serial"
-        # pytest -m "serial"
-        pytest -n auto
+        pytest -n auto -m "not serial"
+        pytest -m "serial"
     - name: Check if cog needs to be run
       run: |
         cog --check docs/*.rst