Fix test for RT #68136

... Mouq++ for pointing out the correct syntax

S14-roles/parameterized-type.t

@@ -60,10 +60,9 @@ dies_ok { R2[C3].new.call_fail },  'classes being used as type constraints insid
 eval_dies_ok 'role ABCD[EFGH] { }', 'role with undefined type as parameter dies';
 
 # RT #68136
-#?rakudo skip 'cannot easily override [] at the moment'
 {
     role TreeNode[::T] does Positional {
-        has TreeNode[T] @!children handles 'postcircumfix:<[ ]>'; # METHOD TO SUB CASUALTY
+        has TreeNode[T] @!children handles <AT-POS ASSIGN-POS BIND-POS>;
         has T $.data is rw;
     };
     my $tree = TreeNode[Int].new;