[perl #125482] [BUG] Signature stringifies the `;;` as a comma in Rakudo

[Christian Bartolomaeus via RT]

I added a test to 06-signature/introspection.t with commit 
https://github.com/perl6/roast/commit/9a4daf7f91

Please note that the output no longer contains the type Any:

$ perl6-m -e 'sub foo($a;; $b) { say "OH HAI" }; foo(1, 2); say &foo.signature'
OH HAI
($a;; $b)

I'm closing this ticket as resolved.