flatmap description is wrong

[smls]

https://docs.perl6.org/type/List#method_flatmap incorrectly suggests that flatmap flattenes the input list before iterating it, when in fact it seems to flatten the result of the map operation:

dd ((1, 2), <a b>).map({ $_, $_ });      # (((1, 2), (1, 2)), (("a", "b"), ("a", "b"))).Seq
dd ((1, 2), <a b>).flatmap({ $_, $_ });  # (1, 2, 1, 2, "a", "b", "a", "b").Seq

The example given on the page should be removed altogether, as it lies about &uc being called four times (it's called twice, once for each element of the input list), and doesn't produce a nested output so there's nothing to flatten, and thus fails to demonstrate what flatmap actually does.

[samcv]

Fixed after a year! Yay! 🎉 🎈