[pt] Fix typo in pt/lessons/basics/mix-tasks.md (#1960)
[pt] Fix typo in pt/lessons/basics/mix-tasks.md (#1960)


nscyclone/elixir-school,doomspork/elixir-school,doomspork/elixir_school,nscyclone/elixir-school,doomspork/elixir-school,nscyclone/elixir-school,doomspork/elixir_school,nscyclone/elixir-school,doomspork/elixir_school,doomspork/elixir-school