[ConstraintSystem] Resolve dependent member as a hole if base is one

Instead of preserving unresolved dependent member types, let's resolve
them as holes if their base has been determined to be one.

lib/Sema/CSSimplify.cpp

@@ -4274,8 +4274,7 @@ bool ConstraintSystem::repairFailures(
     // it's going to be diagnosed by specialized fix which deals
     // with generic argument mismatches.
     if (matchKind == ConstraintKind::BindToPointerType) {
-      auto *member = rhs->getAs<DependentMemberType>();
-      if (!(member && member->getBase()->hasPlaceholder()))
+      if (!rhs->isPlaceholder())
         break;
     }