Bump @backstage/plugin-search-backend-module-pg in /backstage

Bumps [@backstage/plugin-search-backend-module-pg](https://github.com/backstage/backstage/tree/HEAD/plugins/search-backend-module-pg) from 0.5.14 to 0.5.15.
- [Release notes](https://github.com/backstage/backstage/releases)
- [Changelog](https://github.com/backstage/backstage/blob/master/plugins/search-backend-module-pg/CHANGELOG.md)
- [Commits](https://github.com/backstage/backstage/commits/HEAD/plugins/search-backend-module-pg)

---
updated-dependencies:
- dependency-name: "@backstage/plugin-search-backend-module-pg"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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