isosize: stop unmeaningful printing errno message

Earlier printout had strange looking 'Success'.

$ isosize --sectors /dev/urandom
isosize: /dev/urandom: might not be an ISO filesystem
isosize: 733error: le=-1971599244 be=1633181607: Success
...

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

disk-utils/isosize.c

@@ -84,7 +84,7 @@ static int isonum_733(unsigned char *p, int xflag)
 	int be = isonum_732(p + 4);
 	if (xflag && le != be)
 		/* translation is useless */
-		warn("733error: le=%d be=%d", le, be);
+		warnx("733error: le=%d be=%d", le, be);
 	return (le);
 }