Do not throw exception in order producer demo.

[ShannonDing]

UnsupportedEncodingException should not be throw out in main function.

public static void main(String[] args) throws UnsupportedEncodingException 

https://github.com/apache/rocketmq/blob/develop/example/src/main/java/org/apache/rocketmq/example/ordermessage/Producer.java

[alexcao2018]

Please assigned it to me, i want to try it.

[Aaron-TangCode]

Please assigned it to me, thanks!!

[ShannonDing]

Please assigned it to me, i want to try it.

welcome, pls create a PR after you fix it.

[alexcao2018]

fixed #5138.

[alexcao2018]

Having reviewed the other code like this, I also found some issue like this, https://github.com/apache/rocketmq/blob/develop/example/src/main/java/org/apache/rocketmq/example/simple/AsyncProducer.java

[alexcao2018]

Fixed all code in example package like this.

[lizhanhui]

UnsupportedEncodingException should not be throw out in main function.

What is the rational behind this decision?