restore(8) doesn't need to be setgid `tty', and never did.

At the times, restore(8) and rrestore(8) were the different
utilities.  rrestore(8) was installed setuid `root', while
restore(8) with usual ownership and privileges.  Later on,
on August 28, 1991 (what a coincidence!), rrestore(8) code
was merged with restore(8).  The setgid `tty' bit then was
accidentally put.

sbin/restore/Makefile

@@ -7,8 +7,6 @@ CFLAGS+=-DRRESTORE
 CFLAGS+=-I${.CURDIR}/../../libexec/rlogind
 SRCS=	main.c interactive.c restore.c dirs.c symtab.c tape.c utilities.c \
 	dumprmt.c
-BINGRP=	tty
-BINMODE=2555
 MAN=	restore.8
 MLINKS+=restore.8 rrestore.8
 .PATH:	${.CURDIR}/../dump