Bump org.apache.maven.plugins:maven-javadoc-plugin

Bumps [org.apache.maven.plugins:maven-javadoc-plugin](https://github.com/apache/maven-javadoc-plugin) from 3.6.2 to 3.6.3.
- [Release notes](https://github.com/apache/maven-javadoc-plugin/releases)
- [Commits](apache/maven-javadoc-plugin@maven-javadoc-plugin-3.6.2...maven-javadoc-plugin-3.6.3)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-javadoc-plugin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

jvm-packages/xgboost4j/pom.xml

@@ -60,7 +60,7 @@
           <plugin>
               <groupId>org.apache.maven.plugins</groupId>
               <artifactId>maven-javadoc-plugin</artifactId>
-              <version>3.6.2</version>
+              <version>3.6.3</version>
               <configuration>
                   <show>protected</show>
                   <nohelp>true</nohelp>