Remove redundant check in rb_obj_cmp()

* rb_equal() already checks using `obj1 == obj2`.

object.c

@@ -1726,7 +1726,7 @@ rb_obj_not_match(VALUE obj1, VALUE obj2)
 static VALUE
 rb_obj_cmp(VALUE obj1, VALUE obj2)
 {
-    if (obj1 == obj2 || rb_equal(obj1, obj2))
+    if (rb_equal(obj1, obj2))
 	return INT2FIX(0);
     return Qnil;
 }