src/passwd.c: Remove comments about flags that don't exist

Those flags have never existed, AFAICS.

Closes: <https://github.com/shadow-maint/shadow/issues/929>
Cc: Tomas Halman <tomas@halman.net>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

src/passwd.c

@@ -675,14 +675,11 @@ static void update_shadow (void)
  *
  *	-d	delete the password for the named account (*)
  *	-e	expire the password for the named account (*)
- *	-f	execute chfn command to interpret flags
- *	-g	execute gpasswd command to interpret flags
  *	-i #	set sp_inact to # days (*)
  *	-k	change password only if expired
  *	-l	lock the password of the named account (*)
  *	-n #	set sp_min to # days (*)
  *	-r #	change password in # repository
- *	-s	execute chsh command to interpret flags
  *	-S	show password status of named account
  *	-u	unlock the password of the named account (*)
  *	-w #	set sp_warn to # days (*)