Fix issue with c4 dataset creation

[nikita-savelyevv]

What does this PR do?

Condition needs to be updated because if enc.input_ids.shape[1] == seqlen then later the right random bound enc.input_ids.shape[1] - seqlen - 1 equals -1 which leads to an error.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Who can review?

[nikita-savelyevv]

@echarlaix @IlyasMoutawwakil please take a look, thanks!

[HuggingFaceDocBuilderDev]

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[github-actions]

This PR has been marked as stale because it has been open for 90 days with no activity. This thread will be automatically closed in 30 days if no further activity occurs.