Bump src/cohort-extractor from 51c9e7e to eebf491

Bumps [src/cohort-extractor](https://github.com/opensafely-core/cohort-extractor) from `51c9e7e` to `eebf491`.
- [Release notes](https://github.com/opensafely-core/cohort-extractor/releases)
- [Commits](opensafely-core/cohort-extractor@51c9e7e...eebf491)

---
updated-dependencies:
- dependency-name: src/cohort-extractor
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>