Bump org.codehaus.plexus:plexus-xml from 4.0.3 to 4.0.4

Bumps [org.codehaus.plexus:plexus-xml](https://github.com/codehaus-plexus/plexus-xml) from 4.0.3 to 4.0.4.
- [Release notes](https://github.com/codehaus-plexus/plexus-xml/releases)
- [Commits](codehaus-plexus/plexus-xml@plexus-xml-4.0.3...plexus-xml-4.0.4)

---
updated-dependencies:
- dependency-name: org.codehaus.plexus:plexus-xml
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

maven-plugin-testing-harness/pom.xml

@@ -88,7 +88,7 @@ under the License.
       <!-- correct version must be provided by project depends on Maven version -->
       <groupId>org.codehaus.plexus</groupId>
       <artifactId>plexus-xml</artifactId>
-      <version>4.0.3</version>
+      <version>4.0.4</version>
       <optional>true</optional>
     </dependency>