Avoid deprecation warning: List.zip -> Enum.zip (#29)

```
    warning: List.zip/1 is deprecated. Use Enum.zip/1 instead
    │
 78 │     |> List.zip()
    │             ~
    │
    └─ lib/owl/palette.ex:78:13: Owl.Palette.codes/0
```

Enum.zip/1 is safe since forever afaik - only went back to 1.6 https://github.com/elixir-lang/elixir/blob/ddc554a7efef67f16e462709e7f46662f21f7ab5/lib/elixir/lib/enum.ex#L2711

lib/owl/palette.ex

@@ -75,7 +75,7 @@ defmodule Owl.Palette do
     |> List.update_at(-1, fn codes ->
       Enum.concat(codes, List.duplicate("", 15))
     end)
-    |> List.zip()
+    |> Enum.zip()
     |> Enum.map(&Tuple.to_list/1)
     |> Enum.intersperse("\n")
   end