Update the link to the api docs

[warunsl]

The README.md under fass/api-docs has an incorrect URL to the api spec file. This change updates it.

Fixes #1826

Description

Motivation and Context

• [x] I have raised an issue to propose this change (required)
• [ ] My issue has received approval from the maintainers or lead with the design/approved label

How Has This Been Tested?

I imported the updated link in swagger and the api docs show up as expected.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I've read the CONTRIBUTION guide
• [x] I have signed-off my commits with git commit -s
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.