Remove allowedDefaultRefs

[AshotN]

Summary

Currently, if you wish to document a custom method. You have to manually link the ref like this

createSwaggerServiceOptions({
  schemas: { userApproveSchema }
  docs: {
    refs: {
      userApproveRequest: userApproveSchema.$id
    }
  }
})

This PR removes the check that makes that necessary, and custom method Request and Response schemas can be referenced automatically.