Remove Capistrano.

No longer used now that we use Kubernetes to deploy the site instead of
Capistrano.

If you run your own installation of Danbooru, and you used Capistrano to
deploy your site, it is recommended that you switch to either the Docker
Compose file (for personal installs), the Procfile (for non-Dockerized,
development environments), or Kubernetes (for production environments;
see https://github.com/danbooru/danbooru-infrastructure/tree/master/k8s
for Danbooru's production configuration).

config/deploy.rb

@@ -1,27 +0,0 @@
-# This file contains configuration settings for deploying Danbooru to the
-# production servers using Capistrano. This is only used by production and
-# shouldn't be edited by end users.
-#
-# @see Capfile
-# @see config/deploy
-# @see lib/capistrano/tasks
-# @see https://capistranorb.com
-
-set :stages, %w(production test)
-set :default_stage, "test"
-set :application, "danbooru"
-set :repo_url,  "git://github.com/danbooru/danbooru.git"
-set :deploy_to, "/var/www/danbooru2"
-append :linked_dirs, "log", "tmp/pids", "tmp/cache", "tmp/sockets", "vendor/bundle"
-set :branch, ENV.fetch("branch", "master")
-
-# skip migrations if files in db/migrate weren't modified
-set :conditionally_migrate, true
-
-# run migrations on the primary app server
-set :migration_role, :app
-
-set :whenever_roles, :cron
-
-# how long unicorn:legacy_restart (used by deploy:rolling) waits until killing the old unicorn.
-set :unicorn_restart_sleep_time, 10

config/deploy/README.md

@@ -1,14 +0,0 @@
-# Deploy
-
-This directory contains configuration settings for deploying Danbooru to the production servers
-using Capistrano. This is only used by production and shouldn't be edited by end users.
-
-# See also
-
-* [Capfile](../../Capfile)
-* [config/deploy.rb](../deploy.rb)
-* [lib/capistrano/tasks](../../lib/capistrano/tasks)
-
-# External links
-
-* https://capistranorb.com

config/deploy/development.rb

@@ -1,3 +0,0 @@
-set :user, "danbooru"
-set :rails_env, "development"
-server "localhost", :roles => %w(web app db), :primary => true, :user => "danbooru"

config/deploy/production.rb

@@ -1,12 +0,0 @@
-set :user, "danbooru"
-set :rails_env, "production"
-set :delayed_job_workers, 8
-append :linked_files, ".env.production"
-
-server "kagamihara", :roles => %w(web app cron), :primary => true
-server "shima", :roles => %w(web app)
-server "saitou", :roles => %w(web app)
-server "oogaki", :roles => %w(worker)
-
-set :newrelic_appname, "Danbooru"
-after "deploy:finished", "newrelic:notice_deployment"