Remove special case for arguments.toString to match ES5

test/mjsunit/regress/regress-124.js

Index: test/mjsunit/regress/regress-124.js
===================================================================
--- test/mjsunit/regress/regress-124.js	(revision 3077)
+++ test/mjsunit/regress/regress-124.js	(working copy)
@@ -48,9 +48,9 @@
   assertEquals("[object global]", eval("f()"));
 
   // Receiver should be the arguments object here.
-  assertEquals("[object Object]", eval("arguments[0]()"));
+  assertEquals("[object Arguments]", eval("arguments[0]()"));
   with (arguments) {
-    assertEquals("[object Object]", toString());
+    assertEquals("[object Arguments]", toString());
   }
 }