Streamingdataset torch compatibility

[yhl48]

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
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• Did you write any new necessary tests?

What does this PR do?

Fixes #107.

Removed the constraint of having to use torch>=2.1.0 with litdata

[codecov]

Codecov Report

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The diff coverage is 58%.

Additional details and impacted files

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