fix log message in producer example (#960)

Co-authored-by: enes.yalinkaya <enes.yalinkaya@dolap.com>

examples/producer_example/producer_example.go

@@ -101,7 +101,7 @@ func main() {
 
  // Flush and close the producer and the events channel
  for p.Flush(10000) > 0 {
- fmt.Print("Still waiting to flush outstanding messages\n", err)
+ fmt.Print("Still waiting to flush outstanding messages\n")
  }
  p.Close()
 }