Specifically, the "download all artifact from this job ID" and the
"download all artifact from the last successful run of this job name on
this branch name" endpoints allowed this, but the "download a single
artifact file from this job ID" and "download a single artifact file
from the last successful run of this job name on this branch name"
endpoints didn't.

This makes all of them behave the same way with $CI_JOB_TOKEN.