fix(docs): open-api fix for payment response

[srujanchikke]

Type of Change

• [ ] Bugfix
• [ ] New feature
• [ ] Enhancement
• [ ] Refactoring
• [ ] Dependency updates
• [x] Documentation
• [ ] CI/CD

Description

Previous api reference docs : payment response-> payment_method and payment_response>payment_method_type have wrong types, This PR modifies open api spec files.

Additional Changes

• [ ] This PR modifies the API contract
• [ ] This PR modifies the database schema
• [ ] This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

Validate open api spec json check in CI checks.

Checklist

• [x] I formatted the code cargo +nightly fmt --all
• [x] I addressed lints thrown by cargo clippy
• [x] I reviewed the submitted code
• [ ] I added unit tests for my changes where possible