Upgrade http.rb gem to 5.0.4.

Fixes a bug where the Foundation source strategy failed because http.rb
automatically sent a `Content-Length: 0` header with all GET requests,
which caused Foundation to return a 400 Bad Request error. This behavior
was fixed in http.rb 5.x.

http.rb 5.x has a breaking change where it now includes the request object
inside the response object, which we have to handle in a few places.

Gemfile

@@ -30,7 +30,7 @@ gem 'builder'
 gem 'puma'
 gem 'scenic'
 gem 'ipaddress_2'
-gem 'http', "~> 4.4.1"
+gem 'http'
 gem 'activerecord-hierarchical_query', git: "https://github.com/danbooru/activerecord-hierarchical_query"
 gem 'http-cookie', git: "https://github.com/danbooru/http-cookie"
 gem 'pundit'