Previously to query the latest artifacts for a given pipeline we would
include the project ID in the query just in case. However, the inclusion
of this project ID may cause the PostgreSQL query planner to use the
wrong index. For example, it may use
`index_ci_job_artifacts_on_project_id`, which is slow because there may
be thousands of artifacts for a given project.

To optimize this, we can just omit the project ID since we really care
about job artifacts for a given build.

Relates to
https://gitlab.com/gitlab-com/gl-infra/production/-/issues/4674

Changelog: performance