Remove Unicorn.

No longer used now that we use Puma in production. If you still used
Unicorn in your install, switch to `bin/rails server` instead. See
config/puma.rb for config settings.

config.ru

@@ -2,16 +2,5 @@
 
 require_relative "config/environment"
 
-if defined?(Unicorn) && Rails.env.production?
-  # Unicorn self-process killer
-  require 'unicorn/worker_killer'
-
-  # Max requests per worker
-  use Unicorn::WorkerKiller::MaxRequests, 5_000, 10_000
-
-  # Max memory size (RSS) per worker
-  # use Unicorn::WorkerKiller::Oom, (192*(1024**2)), (256*(1024**2))
-end
-
 run Rails.application
 Rails.application.load_server