remove elementary MapSet.size/1 koan

size is covered under koan "However, I do not allow duplication"

lib/koans/09_map_sets.ex

@@ -9,10 +9,6 @@ defmodule MapSets do
     assert Enum.fetch(@set, 0) == {:ok, ___}
   end
 
-  koan "How large is my map set?" do
-    assert MapSet.size(@set) == ___
-  end
-
   koan "However, I do not allow duplication" do
     new_set = MapSet.new([1, 1, 2, 3, 3, 3])
 

test/koans/map_sets_koans_test.exs

@@ -5,7 +5,6 @@ defmodule MapSetsTest do
   test "MapSets" do
     answers = [
       1,
-      5,
       3,
       {:multiple, [false, true]},
       true,