- Remove useless errno.h include

Obtained From: DragonFlyBSD
Index: src/bin/rmdir/rmdir.c
===================================================================
--- src/bin/rmdir/rmdir.c	(revision 90)
+++ src/bin/rmdir/rmdir.c	(working copy)
@@ -42,7 +42,6 @@
 __FBSDID("$FreeBSD: src/bin/rmdir/rmdir.c,v 1.19 2004/11/20 00:41:08 ru Exp $");
 
 #include <err.h>
-#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>