fix: Remove argumentError doctest

[jonathanstiansen]

First, the test itself should work because the character has a :name, so I can't get that test to "pass". When changing it so it does throw an error, the whole liveview process throws an error:

Options I attempted:

1. I tried the original with no name passed to the struct
2. I tried using assert_raise with the third param, including the message but isn't required and made the test long (and still failed)
3. I tried to use assert_raise as well but the argument error is still propagated to the livebook, and kills compilation.

  iex> assert_raise ArgumentError, fn -> %Character{} end
  :ok

[BrooklinJazz]

There's a CI issue I should be able to fix fairly easily when I have time. Since it is an improvement, I'm going to merge this in. Thank you, @jonathanstiansen, for the catch!