Improve example. The showcased construct is redundant with the constr…

…aint.

Removed the constraint.

lib/Language/objects.pod

@@ -102,7 +102,7 @@ sub f(Int $x) {
 Although, in most cases, the L<C<.isa>|isa> method will suffice:
 
 =for code :allow<B L>
-sub f(Int $x) {
+sub f($x) {
     if $xB<.L<isa>>(Int) {
         ...
     }