[JP] Fix a wording in plug.md (#641)
[JP] Fix a wording in plug.md (#641)

Apply #283 changes
psantos10/elixir-school,holsky/elixir-school,yuriibodarev/elixir-school,erickgnavar/elixir-school,erickgnavar/elixir-school,huydx/elixir-school,holsky/elixir-school,huydx/elixir-school,ElixirVietnam/elixir-school,huydx/elixir-school,yuriibodarev/elixir-school,doomspork/elixir-school,doomspork/elixir_school,doomspork/elixir_school,psantos10/elixir-school,nscyclone/elixir-school,ElixirVietnam/elixir-school,nscyclone/elixir-school,doomspork/elixir-school,nscyclone/elixir-school,ElixirVietnam/elixir-school,doomspork/elixir_school,psantos10/elixir-school,holsky/elixir-school,erickgnavar/elixir-school,yuriibodarev/elixir-school,nscyclone/elixir-school,doomspork/elixir-school