[AST] Fix circular reference with implicit some

Only retrieve parsed opaque generic parameters and not
synthsized opaque generic parameters.

Author: angela-laar

lib/AST/ASTScopeCreation.cpp

@@ -901,7 +901,7 @@ namespace {
       }
     }
 
-    return decl->getGenericParams();
+    return decl->getParsedGenericParams();
   }
 }