Fix dangling batch normalization for twisted Edwards curves

[weikengchen]

Description

It is discovered that Pedersen commitments are failing. After some debugging, we confirm that it is because normalize_batch, different from batch_normalize, returns the results instead of applying the mutation directly.

This PR fixes so.

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• [x] Targeted PR against correct branch (master)
• [x] Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
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N/A:

• [ ] Wrote unit tests
• [ ] Updated relevant documentation in the code
• [ ] Added a relevant changelog entry to the Pending section in CHANGELOG.md

[weikengchen]

There appears to be another bug regarding Montgomery representations. Will do in a separate PR.