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

[jtpio]

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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 :+1:

Originally posted by @jtpio in https://github.com/jupyter/notebook/pull/7446#discussion_r1749992141