b56b3d75b0
This fixes a regression since
340eac01f7,
from which we compared function parameter types with cv-qualifiers taken
into account. However, as per [dcl.fct]/p5:
> After producing the list of parameter types, any top-level
cv-qualifiers modifying
> a parameter type are deleted when forming the function type.
Thus, I think we should use `hasSameUnqualifiedType` for type
comparison.
This fixes https://github.com/llvm/llvm-project/issues/75404.