Bump spring-boot-autoconfigure in /1.x/spring-boot-multi-mongodb

Bumps [spring-boot-autoconfigure](https://github.com/spring-projects/spring-boot) from RELEASE to 2.5.15.
- [Release notes](https://github.com/spring-projects/spring-boot/releases)
- [Commits](https://github.com/spring-projects/spring-boot/commits/v2.5.15)

---
updated-dependencies:
- dependency-name: org.springframework.boot:spring-boot-autoconfigure
  dependency-type: direct:production
...

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