fix javadoc warnings

Signed-off-by: Kaushal Kumar <ravi.kaushal97@gmail.com>

server/src/main/java/org/opensearch/search/backpressure/SearchBackpressureService.java

@@ -256,9 +256,9 @@ void doRun() {
     /**
      * Had to define this method to help mock this static method to test the scenario where SearchTraffic should not be
      * penalised when not breaching the threshold
-     * @param searchTasks
-     * @param threshold
-     * @return
+     * @param searchTasks inFlight co-ordinator requests
+     * @param threshold   miniumum  jvm allocated bytes ratio w.r.t. available heap
+     * @return a boolean value based on whether the threshold is breached
      */
     boolean isHeapUsageDominatedBySearch(List<CancellableTask> searchTasks, double threshold) {
         return HeapUsageTracker.isHeapUsageDominatedBySearch(searchTasks, threshold);
@@ -299,8 +299,8 @@ private List<TaskCancellation> addResourceTrackerBasedCancellations(
 
     /**
      * Method to reduce the taskCancellations into unique bunch
-     * @param taskCancellations
-     * @return
+     * @param taskCancellations all task cancellations
+     * @return unique task cancellations
      */
     private List<TaskCancellation> mergeTaskCancellations(final List<TaskCancellation> taskCancellations) {
         final Map<Long, TaskCancellation> uniqueTaskCancellations = new HashMap<>();

server/src/main/java/org/opensearch/search/backpressure/trackers/TaskResourceUsageTrackers.java

@@ -111,7 +111,7 @@ public Optional<TaskCancellation.Reason> checkAndMaybeGetCancellationReason(Task
         /**
          * Method to get taskCancellations due to this tracker for the given {@link CancellableTask} tasks
          * @param tasks cancellation eligible tasks due to node duress and search traffic threshold breach
-         * @return
+         * @return the list of tasks which are breaching task level thresholds for this {@link TaskResourceUsageTracker}
          */
         public List<TaskCancellation> getTaskCancellations(List<CancellableTask> tasks) {
             return tasks.stream()