Several APIs methods respond with content-type text/plain

The GET of the following API methods responds with JSON, but has `Content-Type` header set to `text/plain; charset=utf-8` regardless of the `Accepts` header of the request

`/api/v1/teams/main/pipelines/:pipeline_name/jobs`
`/api/v1/teams/main/pipelines/:pipeline_name/jobs/:job_name/builds`

A PR is forthcoming.

