Update README for link checker (again)
Update README for link checker (again)

Update the README for the link checker: fix a typo introduced in the
previous commit.

au-research/ANDS-ResearchData-Registry,au-research/ANDS-ResearchData-Registry,au-research/ANDS-ResearchData-Registry,au-research/ANDS-ResearchData-Registry,au-research/ANDS-ResearchData-Registry