The gsactions/dco-check action repository was deleted, causing every DCO
workflow run to fail with startup_failure. Replace it with
contributor-assistant/github-action pinned to a commit SHA, matching the
pattern used by NVIDIA-NeMo/DataDesigner.
Signed-off-by: John Myers <johntmyers@users.noreply.github.com>
Co-authored-by: John Myers <johntmyers@users.noreply.github.com>