[JP] Improve translation in metaprogramming lesson (#458)
[JP] Improve translation in metaprogramming lesson (#458)

* strip unnecessary comments
* Make some expressions more natural
yuriibodarev/elixir-school,huydx/elixir-school,psantos10/elixir-school,erickgnavar/elixir-school,doomspork/elixir-school,doomspork/elixir-school,doomspork/elixir_school,doomspork/elixir_school,nscyclone/elixir-school,erickgnavar/elixir-school,ElixirVietnam/elixir-school,holsky/elixir-school,huydx/elixir-school,huydx/elixir-school,erickgnavar/elixir-school,doomspork/elixir-school,holsky/elixir-school,nscyclone/elixir-school,doomspork/elixir_school,ElixirVietnam/elixir-school,psantos10/elixir-school,yuriibodarev/elixir-school,ElixirVietnam/elixir-school,nscyclone/elixir-school,holsky/elixir-school,psantos10/elixir-school,nscyclone/elixir-school,yuriibodarev/elixir-school