gitlab-ci: Fix triggering updates when auth is required

When retrieving an artifacts from a past job with a job token, the
`JOB-TOKEN``header should be used rather than the `PRIVATE-HEADER` and
the API URL should be used rather than the enduser route.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

.gitlab-ci.yml

@@ -227,7 +227,9 @@ trigger-updates:
       if [ -n "$TRIGGER_FROM_JOB" ]
       then
         echo "Retrieving updatable packages from job $TRIGGER_FROM_JOB"
-        wget --header "PRIVATE-TOKEN: $CI_JOB_TOKEN" "$CI_PROJECT_URL/-/jobs/$TRIGGER_FROM_JOB/artifacts/raw/packaging-updates.yaml"
+        JOB_ID=${TRIGGER_FROM_JOB##*/}
+        JOB_API_URL=$CI_API_V4_URL/projects/$CI_PROJECT_ID/jobs/$JOB_ID/
+        wget --header "JOB-TOKEN: $CI_JOB_TOKEN" "$JOB_API_URL/artifacts/packaging-updates.yaml"
       fi
     - |
       if [ -z "$TRIGGER_UPDATES" ]