Turn back on notebook tests

[sserita]

Currently, the notebook tests are off on beta and master with a comment that they started failing in May 2024. We should re-evaluate those failures and turn these tests back on.

[coreyostrove]

Additional context (clawed deep from memory): IIRC these didn't start failing because of any code changes we made directly, but rather because for whatever reason some cells started randomly taking forever to run, eventually timing out. We concluded that the most likely explanation (since none of the devs at the time could reproduce the behavior locally) was that some combination of package versions being installed on the runners was colliding in a manner that behaved badly. We spent a while comparing pip installation logs from before and after this issue started and didn't make any headway at that time. If our hypothesis was correct then this is a prime candidate for an issue that would have magically fixed itself given enough time.