Bump xmlunit-matchers from 2.6.4 to 2.9.1

Bumps [xmlunit-matchers](https://github.com/xmlunit/xmlunit) from 2.6.4 to 2.9.1.
- [Release notes](https://github.com/xmlunit/xmlunit/releases)
- [Changelog](https://github.com/xmlunit/xmlunit/blob/main/RELEASE_NOTES.md)
- [Commits](xmlunit/xmlunit@v2.6.4...v2.9.1)

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

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

pom.xml

@@ -276,7 +276,7 @@
       <dependency>
         <groupId>org.xmlunit</groupId>
         <artifactId>xmlunit-matchers</artifactId>
-        <version>2.6.4</version>
+        <version>2.9.1</version>
       </dependency>
     </dependencies>
   </dependencyManagement>