Remove independent mysql jdbc driver statement. reviewed by @zhouxinyu

NOTICE

@@ -2,7 +2,4 @@ RocketMQ
 Copyright 2016 Alibaba Group.
 
 This product includes software developed at
-The Apache Software Foundation (http://www.apache.org/).
-
-This distribution has producerGroup binary dependency on mysql-connector-java, which is available under gpl 2.0.
-The source code of mysql-connector-java can be found at http://dev.mysql.com/downloads/connector/reconsumeTimes/.
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+The Apache Software Foundation (http://www.apache.org/).
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