Minor changes to populateKinship.r

[bbimber]

@labkey-martyp: this adds a few minor changes to kinship. it:

• MIN_COEFFICIENT was a non-used constant. This promotes it to a script argument. It's still not used by the pipeline. This would make it easier in the future for a java-only PR to pass this if there is a reason to support it.
• This write a TSV with the FamilyIds. This is mostly a QC step if we need to debug anything.

[github-actions]

ERROR: A pull request from 26.7_fb_kinshipOptmization2 is expected to target release26.7-SNAPSHOT, not 26.7_fb_kinshipOptmization