Fix typo in Agent docs
Fix typo in Agent docs

Replace reference to GenEvent with reference to Agent

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