Bump xmlunit.version from 2.9.0 to 2.9.1 (#7576)

Bumps `xmlunit.version` from 2.9.0 to 2.9.1.

Updates `xmlunit-core` from 2.9.0 to 2.9.1
- [Release notes](https://github.com/xmlunit/xmlunit/releases)
- [Changelog](https://github.com/xmlunit/xmlunit/blob/main/RELEASE_NOTES.md)
- [Commits](https://github.com/xmlunit/xmlunit/compare/v2.9.0...v2.9.1)

Updates `xmlunit-matchers` from 2.9.0 to 2.9.1
- [Release notes](https://github.com/xmlunit/xmlunit/releases)
- [Changelog](https://github.com/xmlunit/xmlunit/blob/main/RELEASE_NOTES.md)
- [Commits](https://github.com/xmlunit/xmlunit/compare/v2.9.0...v2.9.1

)

---
updated-dependencies:
- dependency-name: org.xmlunit:xmlunit-core
  dependency-type: direct:development
  update-type: version-update:semver-patch
- dependency-name: org.xmlunit:xmlunit-matchers
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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