[Minor] Fix incorrect warning log

The warning log looks incorrect. Just fix it.

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #4360 from viirya/fixing_typo and squashes the following commits:

48fbe4f [Liang-Chi Hsieh] Fix incorrect warning log.

streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverTracker.scala

@@ -254,7 +254,7 @@ class ReceiverTracker(ssc: StreamingContext, skipReceiverLaunch: Boolean = false
 
       // Check if all the receivers have been deregistered or not
       if (!receiverInfo.isEmpty) {
-        logWarning("All of the receivers have not deregistered, " + receiverInfo)
+        logWarning("Not all of the receivers have deregistered, " + receiverInfo)
       } else {
         logInfo("All of the receivers have deregistered successfully")
       }