Move koan about keyword lists as arguments to the function koan

lib/koans/07_keyword_lists.ex

@@ -31,17 +31,4 @@ defmodule KeywordLists do
 
     assert_raise ArgumentError, fn -> not_kw_list[___] end
   end
-
-  koan "Conveniently keyword lists can be used for function options" do
-    transform = fn str, opts ->
-      if opts[:upcase] do
-        String.upcase(str)
-      else
-        str
-      end
-    end
-
-    assert transform.("good", upcase: true) == ___
-    assert transform.("good", upcase: false) == ___
-  end
 end

lib/koans/13_functions.ex

@@ -97,4 +97,17 @@ defmodule Functions do
 
     assert result == ___
   end
+
+  koan "Conveniently keyword lists can be used for function options" do
+    transform = fn str, opts ->
+      if opts[:upcase] do
+        String.upcase(str)
+      else
+        str
+      end
+    end
+
+    assert transform.("good", upcase: true) == ___
+    assert transform.("good", upcase: false) == ___
+  end
 end