Add left out clarification in Enumerable count (#10560)
Add left out clarification in Enumerable count (#10560)

Mention that when we say that "you can count" is
without traversing the whole collection.
This was left out in 4a1e4481a3714cc48597b6f55242ca6413cade4d
kimshrier/elixir,elixir-lang/elixir,ggcampinho/elixir,kimshrier/elixir,pedrosnk/elixir,joshprice/elixir,kelvinst/elixir,kelvinst/elixir,ggcampinho/elixir,michalmuskala/elixir,pedrosnk/elixir