Upgrade mysql-connector-java version to fix possible transaction rollback failure issue (#4425)
* add tech-support-qq-4.png
* Update README.md
* Enhance the user experience in the scenario of submitting duplicate keys
* Modify the key-value conflict exception prompt, adjust the code style
* Upgrade mysql-connector-java version to fix possible transaction rollback failure issue
* doc(CHANGES.md): update CHANGES.md
Co-authored-by: Jason Song <nobodyiam@gmail.com>