Fix captureWildcards with FlexibleType

[noti0na1]

Apply captureWildcards inside FlexibleType as well

import java.util.stream._

val seqStream: Stream[String] = ???
val shouldNotNPE = seqStream.collect(Collectors.toList())

cc @HarrisL2

[olhotak]

Otherwise LGTM.

[olhotak]

For this one, I don't understand why the other cases are not needed (i.e. what makes FlexibleType special). For example, what if you get the right AppliedType under an AnnontatedType? In that case, this method won't find it either.

But the case for FlexibleType looks right to me.

[noti0na1]

The real fix is in captureWildcards. I guess hasCaptureConversionArg is only used to check top-level AppliedType of a tree for error messages. Maybe adding a stripped after tp can handle more cases, idk. Given the places where FlexibleType is expected to appear, I just added this case.