Bump org.hibernate:hibernate-entitymanager (#4134)

Bumps [org.hibernate:hibernate-entitymanager](https://github.com/hibernate/hibernate-orm) from 5.6.12.Final to 5.6.15.Final.
- [Release notes](https://github.com/hibernate/hibernate-orm/releases)
- [Changelog](https://github.com/hibernate/hibernate-orm/blob/5.6.15/changelog.txt)
- [Commits](hibernate/hibernate-orm@5.6.12...5.6.15)

---
updated-dependencies:
- dependency-name: org.hibernate:hibernate-entitymanager
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]