[fix] Correct the SendAsync() description (#1066)
### Motivation
After #1029 , `eventChan` is split into `dataChan` and `cmdChan`. But the description of `SendAsync()` is not modified.
https://github.com/apache/pulsar-client-go/blob/9867c29ca329302e97ddd9c6a99f66853c7f447f/pulsar/producer.go#L226-L231
### Modifications
- Correct the description of SendAsync() description
(cherry picked from commit 50015d30b807d47d0f7db25d79662817c9f4649e)
diff --git a/pulsar/producer.go b/pulsar/producer.go
index 8fcb891..70d152c 100644
--- a/pulsar/producer.go
+++ b/pulsar/producer.go
@@ -224,8 +224,7 @@
Send(context.Context, *ProducerMessage) (MessageID, error)
// SendAsync a message in asynchronous mode
- // This call is blocked when the `event channel` becomes full (default: 10) or the
- // `maxPendingMessages` becomes full (default: 1000)
+ // This call is blocked when the `maxPendingMessages` becomes full (default: 1000)
// The callback will report back the message being published and
// the eventual error in publishing
SendAsync(context.Context, *ProducerMessage, func(MessageID, *ProducerMessage, error))
