Timing hacks in createDropDownComponent and useEventRefresh tests

[jameswilddev]

There are a few instances of the following in the createDropDownComponent and useEventRefresh tests:

  // Some aspect of unmounting seems to be asynchronous in this test, and not
  // waiting seems to mean that window dimension changes in other tests trigger
  // changes here.
  await new Promise((resolve) => setTimeout(resolve, 10));

It would be ideal if these could be eliminated somehow.