Remove redundant connection check in send function.

The connection check is performed in the c.Reset call just before the c.checkconn call, making this redundant. Removing it simplifies the code and eliminates unnecessary error handling for connection status. This change helps improve code maintainability.

client.go

@@ -1276,12 +1276,6 @@ func (c *Client) sendSingleMsg(message *Msg) error {
 			affectedMsg: message,
 		}
 	}
-	if err = c.checkConn(); err != nil {
-		return &SendError{
-			Reason: ErrConnCheck, errlist: []error{err}, isTemp: isTempError(err),
-			affectedMsg: message,
-		}
-	}
 	return nil
 }