libutil: Remove manual link for nonexistent function

I believe quota_statfs() was the original name of the function now
called quota_check_path(). I must have forgotten to update the MLINK
when I renamed it.

MFC after: 1 week
Fixes: 5666aadb3ddf ("Further extend the quotafile API.")
Fixes: 22afc767869a ("libutil: Add missing MLINKs")
Reviewed by: bcr
Differential Revision: https://reviews.freebsd.org/D51863