Update UMI OpenAPI link to point to API Server's

[nascentcore-eng]

Is your feature request related to a problem? Please describe. Right now the OpenAPI link points to a sample Swagger def, which is not the right one for the API Server.

Describe the solution you'd like Update to point to /swagger/index.html

Are you on Kubernetes, if so, what version Not relevant

Kernel version Not relevant

Describe alternatives you've considered None

Additional context None

[nascentcore-eng]

It seems this OpenAPI link does not appear on @yaxiong-zhao 's API Server instance. Need investigation @zhoujie16 (after we finished API Server & UI integration)