fix(IEx.pry/1): remove unreachable code (#4525)
fix(IEx.pry/1): remove unreachable code (#4525)

It seems like the "IEx cannot pry the shell itself" limitation was
removed 3 years ago in 0b624fff3964853a73e7f9c3c704eff8ecf613bc but this
code wasn't removed.

Found this thanks to Dialyzer and https://github.com/fishcakez/dialyze.

The error printed by Dialyzer was:

> lib/iex.ex:443: The pattern {'error', 'self'} can never match the type 'ok' | {'error','no_iex' | 'refused'}
ggcampinho/elixir,antipax/elixir,elixir-lang/elixir,pedrosnk/elixir,beedub/elixir,lexmag/elixir,gfvcastro/elixir,kimshrier/elixir,michalmuskala/elixir,kimshrier/elixir,kelvinst/elixir,beedub/elixir,pedrosnk/elixir,lexmag/elixir,gfvcastro/elixir,joshprice/elixir,ggcampinho/elixir,antipax/elixir,kelvinst/elixir