Bump sulu/sulu from 2.5.14 to 2.5.15

Bumps [sulu/sulu](https://github.com/sulu/sulu) from 2.5.14 to 2.5.15.
- [Release notes](https://github.com/sulu/sulu/releases)
- [Commits](sulu/sulu@2.5.14...2.5.15)

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

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