Fix tiny typo? terminius

[Kazuki Higashiguchi]

There may be a tiny mis typo 'terminius' instead of 'terminus' in draft-inadarei-api-health-check-02.html#status.

ref: https://github.com/godaddy/terminus
ref: https://tools.ietf.org/id/draft-inadarei-api-health-check-02.html#status

[Irakli Nadareishvili]

Fixed. Thank you