Fix cluster command message

Author: alex-setyawan

src/main/java/seedu/address/logic/commands/ClusterCommand.java

@@ -18,8 +18,7 @@ public class ClusterCommand extends Command {
     public static final String COMMAND_WORD = "cluster";
 
     public static final String MESSAGE_USAGE = COMMAND_WORD + ":\nDetects if there is a cluster of the size given,"
-            + " at the location given, of the disease given, and shows the details of all there with the disease."
-            + "by the respective NRIC in the displayed person list.\n"
+            + " at the location given, of the disease given, and shows the details of all there with the disease.\n"
             + "Parameters: [CLUSTER SIZE] "
             + "[" + PREFIX_ADDRESS + "LOCATION] "
             + "[" + PREFIX_DIAGNOSIS + "DISEASE]\n"