Remove duplicated Javadoc

as proposed by @jglick

core/src/main/java/hudson/PluginWrapper.java

@@ -497,7 +497,6 @@ public class PluginWrapper implements Comparable<PluginWrapper>, ModelObject {
 
     /**
      * Returns the minimum Java version of this plugin.
-     * @return the minimum Java version of this plugin.
      *
      * @since TODO
      */

core/src/main/java/hudson/model/UpdateSite.java

@@ -1128,9 +1128,6 @@ public class UpdateSite {
 
         /**
          * Returns true iff the plugin declares a minimum Java version and it's newer than what the Jenkins master is running on.
-         *
-         * @return true iff the plugin declares a minimum Java version and it's newer than what the Jenkins master is running on.
-         *
          * @since TODO
          */
         public boolean isForNewerJava() {
@@ -1159,9 +1156,6 @@ public class UpdateSite {
 
         /**
          * Returns the minimum Java version needed to use the plugin and all its dependencies.
-         *
-         * @return the minimum Java version needed to use the plugin and all its dependencies.
-         *
          * @since TODO
          */
         @CheckForNull