jobs/test-override: run cosa fetch with --with-cosa-overrides

Otherwise, if the override we're testing is pulling in new
dependencies, we won't know to fetch them. This came up in
https://bodhi.fedoraproject.org/updates/FEDORA-2024-969f546f80 which is
adding a dep on `composefs`.

This also matches CI in the coreos/fedora-coreos-config repo.

(Aside: we've talked in the past about getting notified when new deps
are added and the previous behaviour coincidentally did that, but this
doesn't seem like the right place for it; we shouldn't block packages
from entering Fedora on that account. That check probably belongs in
`bump-lockfile` instead).

Author: jlebon

jobs/test-override.Jenkinsfile

@@ -192,7 +192,7 @@ try {
                     autolock_arg = "--autolock ${build_lock}"
                 }
                 stage("${arch}:Fetch") {
-                    shwrap("cosa fetch ${autolock_arg}")
+                    shwrap("cosa fetch --with-cosa-overrides ${autolock_arg}")
                 }
                 stage("${arch}:Build") {
                     shwrap("cosa build ${autolock_arg}")