Remove reference to old RT

The example works, the RT is closed, the note does nothing.

Fixes #623

Author: coke

doc/Language/operators.pod6

@@ -174,8 +174,6 @@ autovivified if possible.
     $a min= 5; # still 3
     $a min= 2; # 2
 
-Z<blocked by #63642 my @a = 1,2; @a ,= 3,4;>
-
 This behavior is automatically extended to include custom-defined infix operators.
 
     sub infix:<space-concat> ($a, $b) { $a ~ " " ~ $b };