Bumps `axon.version` from 4.5.3 to 4.5.4.

Updates `axon-eventsourcing` from 4.5.3 to 4.5.4
- [Release notes](https://github.com/AxonFramework/AxonFramework/releases)
- [Changelog](https://github.com/AxonFramework/AxonFramework/blob/master/axon-4-api-changes.md)
- [Commits](AxonFramework/AxonFramework@axon-4.5.3...axon-4.5.4)

Updates `axon-spring` from 4.5.3 to 4.5.4
- [Release notes](https://github.com/AxonFramework/AxonFramework/releases)
- [Changelog](https://github.com/AxonFramework/AxonFramework/blob/master/axon-4-api-changes.md)
- [Commits](AxonFramework/AxonFramework@axon-4.5.3...axon-4.5.4)

Updates `axon-eventsourcing` from 4.5.3 to 4.5.4
- [Release notes](https://github.com/AxonFramework/AxonFramework/releases)
- [Changelog](https://github.com/AxonFramework/AxonFramework/blob/master/axon-4-api-changes.md)
- [Commits](AxonFramework/AxonFramework@axon-4.5.3...axon-4.5.4)

Updates `axon-spring-boot-starter` from 4.5.3 to 4.5.4
- [Release notes](https://github.com/AxonFramework/AxonFramework/releases)
- [Changelog](https://github.com/AxonFramework/AxonFramework/blob/master/axon-4-api-changes.md)
- [Commits](AxonFramework/AxonFramework@axon-4.5.3...axon-4.5.4)

---
updated-dependencies:
- dependency-name: org.axonframework:axon-eventsourcing
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.axonframework:axon-spring
  dependency-type: direct:development
  update-type: version-update:semver-patch
- dependency-name: org.axonframework:axon-eventsourcing:tests
  dependency-type: direct:development
  update-type: version-update:semver-patch
- dependency-name: org.axonframework:axon-spring-boot-starter
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

- Use a supplier of the Serializer, to ensure XStream isn't on the
classpath when users don't want it
- Log a warning whenever the defaultSerializer is used, since users
should provide their own XStream instance at all times

#133

Add XStream instance to XStreamSerializer construction per new
requirement

#133