added missing project_id on the PipelineInfo struct

[mvisonneau]

I am not sure if it is available in all cases as this struct is being used in various places but at least for Bridge.DownstreamPipeline it is actually the case. eg:

...
"downstream_pipeline": {
  "id": 22074,
  "project_id": 200,
  "sha": "a254644edfc891b618fc8b7c745494fbff389f82",
  "ref": "main",
  "status": "manual",
  "created_at": "2021-05-13T16:03:41.783Z",
  "updated_at": "2021-05-13T16:04:49.039Z",
  "web_url": "https://git.example.com/foo/bar/-/pipelines/22074"
}

[svanharmelen]

LGTM! Thanks @mvisonneau...