[ru] Update basics/mix-tasks.md to 1.0.3 (#2010)
[ru] Update basics/mix-tasks.md to 1.0.3 (#2010)

- Newline all sentences to correspond to English source
- Add and update changed content
doomspork/elixir-school,doomspork/elixir-school,nscyclone/elixir-school,nscyclone/elixir-school,doomspork/elixir-school,nscyclone/elixir-school,doomspork/elixir_school,doomspork/elixir_school,doomspork/elixir_school,nscyclone/elixir-school