Bump pm2 from 5.1.0 to 5.1.1 in /ee/server/services (#23128)

Bumps [pm2](https://github.com/Unitech/pm2) from 5.1.0 to 5.1.1.
- [Release notes](https://github.com/Unitech/pm2/releases)
- [Changelog](https://github.com/Unitech/pm2/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Unitech/pm2/commits/5.1.1

)

---
updated-dependencies:
- dependency-name: pm2
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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