5026: test: improve performance of update_documents.rs r=dureuill a=PedroTurik
# Pull Request
## Related issue
Fixes one item from #4840
## What does this PR do?
- Applies the changes recommended on the issue for `meilisearch/tests/documents/update_documents.rs`
## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?
Thank you so much for contributing to Meilisearch!
Co-authored-by: Pedro Turik Firmino <pedroturik@gmail.com>
