Fix jsonConverter duplicate entry issue in config.sh

When running obam accelerator config.sh multiple times, <sequence key="jsonConverter"/> entry in _cors_request_handler_.xml is repeated. This PR fixes this.

Issue link:

• [CDSToolkit] - Publishing additional 4 records for API invocation when there is an invocation failure #145

Applicable Labels: OB3 Accelerator

Development Checklist

1. Build complete solution with pull request in place.
2. Ran checkstyle plugin with pull request in place.
3. Ran Findbugs plugin with pull request in place.
4. Ran FindSecurityBugs plugin and verified report.
5. Formatted code according to WSO2 code style.
6. Have you verified the PR doesn't commit any keys, passwords, tokens, usernames, or other secrets?
7. Migration scripts written (if applicable).
8. Have you followed secure coding standards in WSO2 Secure Engineering Guidelines?

Testing Checklist

1. Written unit tests.
2. Verified tests in multiple database environments (if applicable).
3. Tested with BI enabled (if applicable).