builtin.conf: set menu corner_radius to 0 in box profile

OSD mesages are floating in exactly the same way as menu, they should be
consistent.

etc/builtin.conf

@@ -84,6 +84,7 @@ osd-border-style=background-box
 osd-outline-size=0
 osd-shadow-offset=4
 script-opt=console-border_size=0
+script-opt=console-corner_radius=0
 script-opt=stats-border_size=0
 
 [sub-box]