Deezer: fix seeking landing short of the requested position (#6174)

# What does this implement/fix?

The chunks per second got truncated before being multiplied with the
seek position, so the further you seek the more it drifts off.

I measured it on some real tracks, seeking to the middle and capped at
5:00: median 1.2s too early, worst case 5.5s on flac and 10.3s on mp3.
Low bitrate flac is hit hardest, it has the fewest chunks per second to
truncate.

Multiplying first fixes it. The chunk index still counts every chunk, so
the blowfish stripe stays aligned.

## Types of changes

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- [x] Bugfix (non-breaking change which fixes an issue) — `bugfix`
- [ ] New feature (non-breaking change which adds functionality) —
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- [ ] Enhancement to an existing feature — `enhancement`
- [ ] New music/player/metadata/plugin provider — `new-provider`
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected) — `breaking-change`
- [ ] Refactor (no behaviour change) — `refactor`
- [ ] Documentation only — `documentation`
- [ ] Maintenance / chore — `maintenance`
- [ ] CI / workflow change — `ci`
- [ ] Dependencies bump — `dependencies`

## Checklist

- [x] The code change is tested and works locally.
- [x] `pre-commit run --all-files` passes.
- [x] `pytest` passes, and tests have been added/updated under `tests/`
where applicable.
- [ ] For changes to shared models, the companion PR in
`music-assistant/models` is linked.
- [ ] For changes affecting the UI, the companion PR in
`music-assistant/frontend` is linked.
- [x] I have read and complied with the project's [AI
Policy](https://github.com/music-assistant/.github/blob/main/AI_POLICY.md)
for any AI-assisted contributions.
- [ ] I have [raised a PR against the documentation
repository](https://github.com/music-assistant/music-assistant.io/blob/main/CONTRIBUTING.md)
targeting the main or beta branch as appropriate.

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Co-authored-by: jdaberkow <[email protected]>