ci: read only nightly artifact-source configuration [skip ci]

Signed-off-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>

Author: rwgk

.github/workflows/ci-nightly.yml

@@ -124,7 +124,7 @@ jobs:
           git fetch --depth=1 origin "$HEAD_SHA"
           snapshot=$(mktemp -d)
           trap 'rm -rf -- "$snapshot"' EXIT
-          git archive "$HEAD_SHA" | tar -x -C "$snapshot"
+          git archive "$HEAD_SHA" ci/versions.yml | tar -x -C "$snapshot"
           python - "$snapshot/ci/versions.yml" <<'PYTHON'
           import os
           import re