GEODE-10356: Corrected the comment (apache#7762)

* The previous comment on removeOldEntry mentioned that the old entry
was replaced
* This has been corrected to mention that the old entry is removed and
the new entry has been added to the region queue

geode-core/src/main/java/org/apache/geode/internal/cache/wan/serial/SerialGatewaySenderQueue.java

@@ -611,7 +611,8 @@ private void removeOldEntry(Conflatable object, Long tailKey) throws CacheExcept
         keepOldEntry = true;
       }
 
-      // Replace the object's value into the queue if necessary
+      // Remove the old entry from the queue if necessary. The new entry is already present
+      // in the queue region.
       if (!keepOldEntry) {
         Conflatable previous = (Conflatable) region.remove(previousIndex);
         stats.decQueueSize(1);