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:		5666aadb3d ("Further extend the quotafile API.")
Fixes:		22afc76786 ("libutil: Add missing MLINKs")
Reviewed by:	bcr
Differential Revision:	https://reviews.freebsd.org/D51863

lib/libutil/Makefile

@@ -136,7 +136,6 @@ MLINKS+=quotafile.3 quota_on.3
 MLINKS+=quotafile.3 quota_open.3
 MLINKS+=quotafile.3 quota_qfname.3
 MLINKS+=quotafile.3 quota_read.3
-MLINKS+=quotafile.3 quota_statfs.3
 MLINKS+=quotafile.3 quota_write_limits.3
 MLINKS+=quotafile.3 quota_write_usage.3
 MAN+=	realhostname.3