Bump org.xmlunit:xmlunit-core from 2.9.0 to 2.10.0 in /formats/xml (#631)

Bumps [org.xmlunit:xmlunit-core](https://github.com/xmlunit/xmlunit) from 2.9.0 to 2.10.0.
- [Release notes](https://github.com/xmlunit/xmlunit/releases)
- [Changelog](https://github.com/xmlunit/xmlunit/blob/main/RELEASE_NOTES.md)
- [Commits](xmlunit/xmlunit@v2.9.0...v2.10.0)

---
updated-dependencies:
- dependency-name: org.xmlunit:xmlunit-core
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

formats/xml/pom.xml

@@ -33,7 +33,7 @@
 
     <properties>
         <module-name>io.cloudevents.formats.xml</module-name>
-        <xmlunit.version>2.9.0</xmlunit.version>
+        <xmlunit.version>2.10.0</xmlunit.version>
         <javax.xml.version>2.3.1</javax.xml.version>
     </properties>