fixed sprintf doc missing $a in order of arguments example

Author: grizzlysmit

doc/Type/Str.pod6

@@ -612,7 +612,7 @@ So:
 uses C<$a> for the width, C<$b> for the precision, and C<$c> as the value to
 format; while:
 
-  NYI sprintf '<%*1$.*s>', $b, 'b';
+  NYI sprintf '<%*1$.*s>', $a, $b, 'b';
 
 would use C<$a> for the width and precision and C<$b> as the value to format.