Fix typo in WerMetric: use hyp_seqs instead of ref_seqs for hyp_seqs_list

[beckybyte]

What does this PR do? Please describe:
Fix a typo in WerMetric.update() where hyp_seqs_list was incorrectly assigned from ref_seqs.cpu().tolist() instead of hyp_seqs.cpu().tolist(). This caused the unit-level edit distance to always compare reference sequences against themselves, making UER always 0 regardless of actual model output.

Does your PR introduce any breaking changes? If yes, please list them:
No breaking changes.

Check list:

• Was the content of this PR discussed and approved via a GitHub issue? (no need for typos or documentation improvements)
• Did you read the contributor guideline?
• Did you make sure that your PR does only one thing instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests?
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (no need for typos, documentation, or minor internal changes)

[meta-cla]

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[Copilot]

Pull request overview

This PR fixes a logic bug in the WerMetric.update() implementation so that unit-level edit distance (UER) is computed against the hypothesis token sequences rather than accidentally comparing references against themselves.

Changes:

• Correct hyp_seqs_list to be derived from hyp_seqs (instead of ref_seqs) before computing edit distance.

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[meta-cla]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks!

[cirquit]

Thanks for the finding this bug and for the contribution!