Simplify modeling_utils.py for DTensor check

[amd-xiaoyu12]

Simplify the condition check, since DTensor is also a Tensor:
if isinstance(tensor, torch.Tensor) or isinstance(tensor, DTensor): =>
if isinstance(tensor, torch.Tensor):

The logic for DTensor export later within this function will handle it.

What does this PR do?

Fixes # (issue)

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