fix: improve error messaging for LRO CancellationException (googleapis#3873)

Author: mpeddada1

gax-java/gax/src/main/java/com/google/api/gax/longrunning/OperationTimedPollAlgorithm.java

@@ -91,7 +91,10 @@ public boolean shouldRetry(TimedAttemptSettings nextAttemptSettings)
     if (LOGGER.isLoggable(Level.WARNING)) {
       LOGGER.log(
           Level.WARNING,
-          "The task has been cancelled. Please refer to "
+          "The long running operation request is no longer being tracked. "
+              + "Possible reasons include a timeout or "
+              + "exceeding the maximum number of poll attempts."
+              + " Please refer to "
               + LRO_TROUBLESHOOTING_LINK
               + " for more information");
     }