Mark API key as required if it is

[lornajane]

We're rendering api_key as a query parameter (I'm looking at https://developer.nexmo.com/api/verify) but not marking it as required. In the Verify API spec, the api_secret parameter has been added as a query parameter to each endpoint since it is otherwise not picked up by other tools. The "correct" way to do this though is as seen in our number-insight spec which lists both api_key and api_secret as security schemes - however these also aren't rendered as required fields which I think they should be.