React Query Fix: Immediately show feedback to student after instructor generated it

[mpetojevic]

• There was a problem with react query where feedback couldn't be properly loaded, because of undefined submission (meaning at the moment where we are trying to access submission, it's still not fully loaded) -> fixed
• When instructor generates feedback for a submission, a refetch on submissions shown to student is enforced, so they see it immediately without a need to reload the page.