UI test for "Redirect paths from the notebooks route to the tree route if they are directories"

[jtpio]

In addition to this test, maybe it could be interesting to add a UI test to mimic real user interactions: https://github.com/jupyter/notebook/tree/main/ui-tests

But we can track that in a separate issue 👍

Originally posted by @jtpio in #7446 (comment)