[AST] Type erase covariant root type params to dependent upper bound

There are two functions that type-erase occurrences of covariant
'Self'-rooted type parameters to their most specific bounds. Update
the second function to erase to the dependent upper bound.

Author: angela-laar

lib/AST/Type.cpp

@@ -587,7 +587,7 @@ Type TypeBase::typeEraseOpenedArchetypesWithRoot(
         erasedTy = root->getExistentialType();
       } else {
         erasedTy =
-            sig->getNonDependentUpperBounds(archetype->getInterfaceType());
+            sig->getDependentUpperBounds(archetype->getInterfaceType());
       }
 
       if (metatypeDepth) {