Update typespec for System.get_env/1 (#5611)
Update typespec for System.get_env/1 (#5611)


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