Bump ash_postgres from 2.4.12 to 2.4.15 in /server

Bumps [ash_postgres](https://github.com/ash-project/ash_postgres) from 2.4.12 to 2.4.15.
- [Changelog](https://github.com/ash-project/ash_postgres/blob/main/CHANGELOG.md)
- [Commits](ash-project/ash_postgres@v2.4.12...v2.4.15)

---
updated-dependencies:
- dependency-name: ash_postgres
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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