notification queue limit has no maxLimit (#9380)

New value defaults to 100K events by default,
but users can tune this value upto any value
they seem necessary.

* increase the limit to maxint64 while validating

pkg/event/target/kafka.go

@@ -110,9 +110,6 @@ func (k KafkaArgs) Validate() error {
 			return errors.New("queueDir path should be absolute")
 		}
 	}
-	if k.QueueLimit > 10000 {
-		return errors.New("queueLimit should not exceed 10000")
-	}
 	if k.Version != "" {
 		if _, err := sarama.ParseKafkaVersion(k.Version); err != nil {
 			return err