remove Cool type constraint from Bool.pick

It doesn't allow a Whatever-star, so it's certainly wrong. It now let the
re-dispatch to Parcel.pick do the type check or coercion, if any.

src/core/Bool.pm

@@ -7,7 +7,7 @@ augment class Bool does Abstraction {
     method Str() { $.perl() }
 
     method Bridge() { self ?? 1.Bridge !! 0.Bridge }
-    method pick(Cool $count = 1, :$replace) {
+    method pick($count = 1, :$replace) {
         (True, False).pick($count, :$replace);
     }
 }