wall: remove unnecessary warning

wall(1) may be used in scripts or in pipe. In this case report failed
ttyname() does not make sense, especially if the code does not depend
on on this function.

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1608176
Signed-off-by: Karel Zak <kzak@redhat.com>

term-utils/wall.c

@@ -359,7 +359,6 @@ static char *makemsg(char *fname, char **mvec, int mvecsz,
 		where = ttyname(STDOUT_FILENO);
 		if (!where) {
 			where = "somewhere";
-			warn(_("cannot get tty name"));
 		} else if (strncmp(where, "/dev/", 5) == 0)
 			where += 5;