Documentation for rocketmq-connector-jdbc should be updated

hi, I found that the source-record-converter field in the rocketmq-connect-jdbc documentation should be consistent with the latest implementation class name in rocketmq-connect-runtime

For example, the source-record-converter class in the document cannot be parsed by the following method in the rocketmq-connect-runtime project, because this class is not a subclass of io.openmessaging.connector.api.data.RecordConverter in the method, and cannot be parsed convert，otherwise there will be a java.lang.ClassCastException problem

The source-record-converter field in the documentation should be updated to the latest **org.apache.rocketmq.connect.runtime.converter.record.json.JsonConverter** class