YARN-9340. [Clean-up] Remove NULL check before instanceof in ResourceRequestSetKey

(Contributed by Shweta Yakkali via Daniel Templeton)

Change-Id: I932e29b36f086f7b7c76a250e33b473617ddbda1

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/scheduler/ResourceRequestSetKey.java

@@ -88,7 +88,7 @@ public class ResourceRequestSetKey extends SchedulerRequestKey {
 
   @Override
   public boolean equals(Object obj) {
-    if (obj == null || !(obj instanceof SchedulerRequestKey)) {
+    if (!(obj instanceof SchedulerRequestKey)) {
       return false;
     }
     if (!(obj instanceof ResourceRequestSetKey)) {