RESTful API doc missing headers for /libpod/build

[etomelleri]

Hello,
I found that in the HTTP API documentation the header parameters for /libpod/build are missing (it is used to send the build context to the podman service). See for comparison the compat API for /build where the header parameters are listed after all the query parameters, just before the responses. I think this is one of the issues reported in #6547:

'Libpod Build Image' has the same issue as the above one and no request samples

[flouthoc]

I can take a look at this.