revert for now, sysmerge needs to create the group first.

found the hard way by deraadt

src/etc/mtree/4.4BSD.dist

@@ -1,4 +1,4 @@
-#	$OpenBSD: 4.4BSD.dist,v 1.304 2019/01/26 10:58:32 florian Exp $
+#	$OpenBSD: 4.4BSD.dist,v 1.305 2019/01/26 12:09:39 florian Exp $
 
 /set type=dir uname=root gname=wheel mode=0755
 
@@ -106,13 +106,6 @@ etc
         lib
         ..
     ..
-
-    # ./etc/unwind
-    unwind
-        trustanchor		gname=_unwind uname=root mode=0775
-        ..
-    ..
-
 ..
 
 # ./home