[infrastructure] Find per-arch preflight results in the Red Hat certify check (#8111)

For a manifest list, preflight writes results.json only under
artifacts/<arch>/. The literal artifacts/results.json path is not a glob,
so nullglob kept it in the list and jq failed on the missing file even
though every check passed. A single globstar pattern matches both layouts.

.github/workflows/redhat-certify.yml

@@ -154,8 +154,8 @@ jobs:
       - name: Fail if any check did not pass
         run: |
           set -euo pipefail
-          shopt -s nullglob
-          results=(artifacts/results.json artifacts/*/results.json)
+          shopt -s nullglob globstar
+          results=(artifacts/**/results.json)
           if [[ ${#results[@]} -eq 0 ]]; then
             echo "::error::preflight produced no results.json"
             exit 1