Tests fix imodel react hooks

[ben-bartholomew]

Some of the tests for useFeatureOverrides in the package imodel-react-hooks were skipped during a previous upgrade. These changes fix and re-enable them.

[CLAassistant]

All committers have signed the CLA.

[MichaelBelousov]

LGTM except I hesitate to let this through without adding a test that confirms there are no longer any feature overrides in the provider list after unmounting...

basically we only test the hook, not the provider. But if someone confirms that it works locally after viewport unmount, then I don't mind skipping adding it for now if it's too much overhead

[ben-bartholomew]

Fixing exists tests that were commented out is one thing, but I don't think I have the bandwidth or the expertise to add a new test that does something like that.

FWIW I gave it a try, but its an internal variable that disappears when the component unmounts; something clever will have to be done to get access to it without exposing it to consumers of the package.