Fix Javadocs for ThreadPool#schedule

This commit fixes an issue with an @throws tag on ThreadPool#schedule
not containing a description.

core/src/main/java/org/elasticsearch/threadpool/ThreadPool.java

@@ -327,7 +327,7 @@ public class ThreadPool extends AbstractComponent implements Closeable {
      * @return a ScheduledFuture who's get will return when the task is has been added to its target thread pool and throw an exception if
      *         the task is canceled before it was added to its target thread pool. Once the task has been added to its target thread pool
      *         the ScheduledFuture will cannot interact with it.
-     * @throws org.elasticsearch.common.util.concurrent.EsRejectedExecutionException
+     * @throws EsRejectedExecutionException if the task cannot be scheduled for execution
      */
     public ScheduledFuture<?> schedule(TimeValue delay, String executor, Runnable command) {
         if (!Names.SAME.equals(executor)) {