always return new list from PySequence_List

Author: tomasstupka

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/PythonCextBuiltins.java

@@ -2733,11 +2733,6 @@ protected boolean isTuple(Object obj, GetClassNode getClassNode) {
     @Builtin(name = "PySequence_List", minNumOfPositionalArgs = 1)
     @GenerateNodeFactory
     public abstract static class PySequenceListNode extends PythonUnaryBuiltinNode {
-        @Specialization
-        public PList values(PList obj) {
-            return obj;
-        }
-
         @Specialization
         public Object values(VirtualFrame frame, Object obj,
                         @Cached ConstructListNode listNode,