Disable old Plantuml plugin due to issues with site generation with n…

…ewer java versions

Error:  Failed to execute goal com.github.jeluard:plantuml-maven-plugin:7954:generate (generate-plantuml-diagrams) on project jaxb2-maven-plugin: Execution generate-plantuml-diagrams of goal com.github.jeluard:plantuml-maven-plugin:7954:generate failed: An API incompatibility was encountered while executing com.github.jeluard:plantuml-maven-plugin:7954:generate: java.lang.IllegalAccessError: class net.sourceforge.plantuml.png.PngIOMetadata (in unnamed module @0xf882465) cannot access class com.sun.imageio.plugins.png.PNGMetadata (in module java.desktop) because module java.desktop does not export com.sun.imageio.plugins.png to unnamed module @0xf882465

pom.xml

@@ -344,6 +344,7 @@
       </plugin>
 
       <!-- Provides PlantUML integration into site deployments. -->
+      <!--
       <plugin>
         <groupId>com.github.jeluard</groupId>
         <artifactId>plantuml-maven-plugin</artifactId>
@@ -374,6 +375,7 @@
           </execution>
         </executions>
       </plugin>
+      -->
     </plugins>
   </build>