YARN-11089. Fix typo in RM audit log. Contributed by Junfan Zhang.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/RMAppManager.java

@@ -294,7 +294,7 @@ public class RMAppManager implements EventHandler<RMAppManagerEvent>,
 
   protected void writeAuditLog(ApplicationId appId) {
     RMApp app = rmContext.getRMApps().get(appId);
-    String operation = "UNKONWN";
+    String operation = "UNKNOWN";
     boolean success = false;
     switch (app.getState()) {
       case FAILED: