remove const cast for DLManagedTensor (microsoft#20015)

### Description
<!-- Describe your changes. -->
Removing const_cast as it might lead to unknown behavior. Specifying
DLMangedTensor as a const doesn't seem to be necessary and I have tested
this by running torch_ort.configure. Not sure what other tests which
needs to be done. Background can be found in this
[PR](microsoft#19982)


### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->

onnxruntime/python/torch_cpp_extensions/aten_op_executor/aten_op_executor.cc

@@ -36,7 +36,7 @@ struct ATenOperator {
   size_t return_size;
   std::vector<c10::TypeKind> ret_kinds;
 
-  c10::IValue ToIValueArgument(const DLManagedTensor* dlpack, size_t index) const {
+  c10::IValue ToIValueArgument(DLManagedTensor* dlpack, size_t index) const {
     TORCH_INTERNAL_ASSERT(index < argument_size);
     bool is_optional = is_optional_arguments[index];
     TORCH_INTERNAL_ASSERT(dlpack || is_optional || default_values[index] ||
@@ -57,7 +57,7 @@ struct ATenOperator {
     c10::IValue i_value;
     // Create the torch tensor from this DLPack no matter we need it or not below,
     // so that the dlpack's deleter will be triggered when torch tensor is out of scope.
-    at::Tensor tensor = at::fromDLPack(const_cast<DLManagedTensor*>(dlpack));
+    at::Tensor tensor = at::fromDLPack(dlpack);
     switch (elem_kinds[index]) {
       case c10::TypeKind::TensorType: {
         i_value = is_optional ? c10::IValue(c10::optional<at::Tensor>(tensor)) : c10::IValue(tensor);