Correct title of section in mix test docs (#9553)
Correct title of section in mix test docs (#9553)


michalmuskala/elixir,pedrosnk/elixir,kelvinst/elixir,pedrosnk/elixir,joshprice/elixir,kimshrier/elixir,elixir-lang/elixir,kimshrier/elixir,kelvinst/elixir,ggcampinho/elixir,ggcampinho/elixir