ci: do not confuse pytest about where ipywidgets is

Author: maartenbreddels

.github/workflows/tests.yml

@@ -109,8 +109,8 @@ jobs:
           SOLARA_TEST_RUNNERS: "jupyter_notebook,jupyter_lab"
         run: |
           pip install pytest
-          cd python/ipywidgets
-          pytest --cov=ipywidgets ipywidgets
+          playwright install
+          pytest --cov=ipywidgets --pyargs ipywidgets
 
   spec:
     name: Message Specification