Bump org.xmlunit:xmlunit-core from 2.8.2 to 2.9.1

Bumps [org.xmlunit:xmlunit-core](https://github.com/xmlunit/xmlunit) from 2.8.2 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@v2.8.2...v2.9.1)

---
updated-dependencies:
- dependency-name: org.xmlunit:xmlunit-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

build.gradle.kts

@@ -68,7 +68,7 @@ dependencies {
     testImplementation("org.junit.jupiter:junit-jupiter-engine:$junit5Version")
     testImplementation("org.junit.jupiter:junit-jupiter-params:$junit5Version")
     testImplementation("com.willowtreeapps.assertk:assertk:0.24")
-    testImplementation("org.xmlunit:xmlunit-core:2.8.2")
+    testImplementation("org.xmlunit:xmlunit-core:2.9.1")
     testImplementation("org.reflections:reflections:0.10.2")
 }