remove const cast for DLManagedTensor (#20015)
### Description
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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](https://github.com/microsoft/onnxruntime/pull/19982)
### Motivation and Context
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- If it fixes an open issue, please link to the issue here. -->
