Fix example $metadata output in Logger.Formatter docs
Fix example $metadata output in Logger.Formatter docs

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