etc: remove leftover leading empty comments, blank lines

Remove leftover empty leading comments/blank lines that had been
spacers between $FreeBSD$ and the following content in config files
in src/etc.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D41548

etc/group

@@ -1,4 +1,3 @@
-#
 wheel:*:0:root
 daemon:*:1:
 kmem:*:2:

etc/mail/Makefile

@@ -1,5 +1,3 @@
-#
-#
 # This Makefile provides an easy way to generate the configuration
 # file and database maps for the sendmail(8) daemon.
 #

etc/master.passwd

@@ -1,4 +1,3 @@
-#
 root::0:0::0:0:Charlie &:/root:/bin/sh
 toor:*:0:0::0:0:Bourne-again Superuser:/root:
 daemon:*:1:1::0:0:Owner of many system processes:/root:/usr/sbin/nologin

etc/mtree/Makefile

@@ -1,4 +1,3 @@
-
 .include <src.opts.mk>
 
 .include <bsd.compat.pre.mk>

etc/mtree/README

@@ -1,4 +1,3 @@
-
 Note: If you modify these files, please keep hier(7) updated!
 
 These files are used to create empty file hierarchies for building the

etc/root/dot.k5login

@@ -1,3 +1,2 @@
-#
 # user1/root@YOUR.REALM.WHEREVER
 # user2/root@YOUR.REALM.WHEREVER

etc/shells

@@ -1,4 +1,3 @@
-#
 # List of acceptable shells for chpass(1).
 # ftpd(8) will not allow users to connect who are not using
 # one of these shells.