The ProfileModal tests would sometimes fail with this error:

```
FAILED TESTS:
  ✖ "after each" hook for "shows modal on "openProfile" event"
    Chrome Headless 129.0.0.0 (Linux x86_64)
  Error: Failed to execute 'showModal' on 'HTMLDialogElement': The element is not in a Document.
```

The `HTMLDialogElement.showModal` call happens in an effect when the
`ModalDialog` component is rendered with the `isClosed` prop set to false. In
the ProfileModal tests, the component was rendered in a disconnected DOM node,
so this error should have happened on every run. However the
`emitter.publish("openProfile")` call which triggered this render was not
wrapped in `act` and so the effect which calls `showModal` was scheduled, but
often did not actually run before the component was unmounted in the `afterEach`
hook.

Fix the issue by:

 - Wrapping all `emitter.publish("openProfile")` calls in `act`, so they
   synchronously execute the effect.
 - Rendering the `ProfileModal` component in a connected DOM container
   which is removed after the test runs
 - For consistency, update the `NotebookModal` tests to work in the same
   way as the ProfileModal tests, with a single container element which
   is removed at the end of the test