ExUnit.Callbacks: improve guards, specs and small docs correction (#5329)
ExUnit.Callbacks: improve guards, specs and small docs correction (#5329)


joshprice/elixir,michalmuskala/elixir,beedub/elixir,lexmag/elixir,elixir-lang/elixir,gfvcastro/elixir,antipax/elixir,beedub/elixir,lexmag/elixir,kelvinst/elixir,ggcampinho/elixir,ggcampinho/elixir,kimshrier/elixir,pedrosnk/elixir,gfvcastro/elixir,antipax/elixir,pedrosnk/elixir,kelvinst/elixir,kimshrier/elixir