Fix body schema for generate user TFA

[joselcvarela]

Currently in the docs it is showing that body must be [string] but it should be

{
  "password": "d1r3ctu5"
}

[vercel]

@joselcvarela is attempting to deploy a commit to the Directus Team on Vercel.

A member of the Team first needs to authorize it.

[rijkvanzanten]

Thanks @joselcvarela! Mind updating it in https://github.com/directus/openapi instead? 🙏🏻