[KO] Translation of Concurrency lesson (#466)
[KO] Translation of Concurrency lesson (#466)

* Translate concurrency lesson

* Apply @riseshia 's suggestion

* Accept @devleoper 's suggestion

doomspork/elixir_school,psantos10/elixir-school,erickgnavar/elixir-school,doomspork/elixir-school,holsky/elixir-school,yuriibodarev/elixir-school,nscyclone/elixir-school,huydx/elixir-school,holsky/elixir-school,erickgnavar/elixir-school,holsky/elixir-school,doomspork/elixir-school,ElixirVietnam/elixir-school,yuriibodarev/elixir-school,yuriibodarev/elixir-school,doomspork/elixir_school,erickgnavar/elixir-school,ElixirVietnam/elixir-school,doomspork/elixir-school,psantos10/elixir-school,ElixirVietnam/elixir-school,huydx/elixir-school,nscyclone/elixir-school,psantos10/elixir-school,nscyclone/elixir-school,doomspork/elixir_school,nscyclone/elixir-school,huydx/elixir-school