Update Rails on Rack guide [ci skip]

[yhirano55]

Summary

The result of bin/rails middleware is different between description of guide and actual logs. So I've fixed it.

This is actual logs:

$ bundle exec rails middleware
use Rack::Sendfile
use ActionDispatch::Static
use ActionDispatch::Executor
use ActiveSupport::Cache::Strategy::LocalCache::Middleware
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use ActionDispatch::RemoteIp
use Sprockets::Rails::QuietAssets
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use WebConsole::Middleware
use ActionDispatch::DebugExceptions
use ActionDispatch::Reloader
use ActionDispatch::Callbacks
use ActiveRecord::Migration::CheckPending
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use Rack::Head
use Rack::ConditionalGet
use Rack::ETag
run MyApp::Application.routes

[rails-bot]

r? @eileencodes

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[prathamesh-sonpatki]

Thanks 👍