Turns out I was right the first time, I was just missing that this
should only be done in MRs, which @daniels added in 16527f6ffd.
Without this, a "farm re-enable" pipeline will run all the jobs for that
farm, but will have none of the container & build jobs to support these
tests.
This reverts commit 1c3097225a.
Fixes: 1c3097225a ("ci: don't run everything just because a farm gets re-enabled")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25243>