build(deps): bump pgvector from 0.3.5 to 0.4.0 in /backend
Bumps [pgvector](https://github.com/pgvector/pgvector-python) from 0.3.5 to 0.4.0.
- [Changelog](https://github.com/pgvector/pgvector-python/blob/master/CHANGELOG.md)
- [Commits](https://github.com/pgvector/pgvector-python/compare/v0.3.5...v0.4.0)
---
updated-dependencies:
- dependency-name: pgvector
dependency-version: 0.4.0
dependency-type: direct:production
update-type: version-update:semver-minor
...
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dependabot[bot]