Remove "bin/repository lookup-users" workflow
Ref T13552. This is one of two callsites to "diffusion.querycommits". It's an old debugging workflow which I haven't used in years and which is likely obsoleted by identities and other changes.
I believe the root problem here was also ultimately user error (a user has misconfigured their local Git author email as another user).
Test Plan: Grepped for "lookup-users", got no hits.
Maniphest Tasks: T13552
Differential Revision: https://secure.phabricator.com/D21444