Use :>! instead of :> for pattern matching Vecs

[martijnbastiaan]

This is used to workaround (spurious) warnings GHC generates on newer versions. Example of such a warning:

example/Example.hs:170:1: error: [GHC-62161] [-Wincomplete-uni-patterns, Werror=incomplete-uni-patterns]
    Pattern match(es) are non-exhaustive
    In a pattern binding:
        Patterns of type ‘BusTag (DF dom Int) (Bwd (DF dom Int))
                          :-> BusTag
                                (Vec 1 (DF dom Int)) (Fwd (Vec 1 (DF dom Int)))’ not matched:
            _ :-> BusTagBundle (Cons _ _)
    |
170 | fanout = circuit $ \a -> do
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^...