[rocketmq-connector-jdbc] Update README.md

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**BUG REPORT**

1. Please describe the issue you observed:

- What did you do (The steps to reproduce)?
Tried to create jdbc source/sink connectors baseing on config template in README.md

- What did you expect to see?
Jdbc connectors are created successfully

- What did you see instead?
Got response "Fail" after calling Restful API

2. Please tell us about your environment:

3. Other information (e.g. detailed explanation, logs, related issues, suggestions how to fix, etc):
The config tamplate in README.md does not fit with request config in code.
Try to understand correct config information by studing code, and update config template in README.md

Start with the jdbc connector README.md configuration template and compare it with the request configuration expected by the connector code. Verify the documented source and sink settings against the RESTful API request format. Done means the README examples match the code and can be used to create both JDBC connectors successfully.

Written by the indexing model from the issue text.