fix test usage: -ot not -older

Reference: /n/atom/patch/applied2013/radarolder
Date: Sun Jun  2 00:01:36 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /rc/bin/radar	Sun Jun  2 00:01:25 2013
+++ /rc/bin/radar	Sun Jun  2 00:01:25 2013
@@ -55,7 +55,7 @@
 	g=$f/$2
 	if(~ $#* 3)
 	if(test -f $f/$2)
-	if(test $f/$2 -older $3)
+	if(test $f/$2 -ot $3)
 		rm $g
 	if(! test -f $f/$2)
 		hget $b/$1 > $g || fail