Even though SO may not be correct
overrides sometimes, it feels more
natural to treat fake overrides as...
well, "overrides". And without it
we'd need to make the code in
`FirOverrideChecker` less intuitive.
Use-site substitution override happens in situations like this:
```
interface List<A> { fun get(i: Int): A }
fun take(list: List<String>) {
list.get(10) // this call
}
```
We want to have those overrides unwrapped, because we don't want
to deal with a different KtSymbol for each possible use-site
^KT-50862 Fixed
Nikolay Lunyak