Remove StorageManager::SFTP.

Remove the SFTP file storage backend. Downstream users can use either
sshfs (which is what Danbooru now uses in production) or rclone instead.
The Ruby SFTP gem was much slower than sshfs.

config/danbooru_default_config.rb

@@ -196,10 +196,6 @@ module Danbooru
       # base_dir - where to store files (default: under public/data)
       # base_url - where to serve files from (default: https://#{hostname}/data)
       StorageManager::Local.new(base_url: "#{Danbooru.config.canonical_url}/data", base_dir: Rails.root.join("public/data"))
-
-      # Store files on one or more remote host(s). Configure SSH settings in
-      # ~/.ssh_config or in the ssh_options param (ref: http://net-ssh.github.io/net-ssh/Net/SSH.html#method-c-start)
-      # StorageManager::SFTP.new("i1.example.com", "i2.example.com", base_dir: "/mnt/backup", ssh_options: {})
     end
 
     # The method to use for backing up image files.
@@ -209,10 +205,6 @@ module Danbooru
 
       # Backup files to /mnt/backup on the local filesystem.
       # StorageManager::Local.new(base_dir: "/mnt/backup")
-
-      # Backup files to /mnt/backup on a remote system. Configure SSH settings
-      # in ~/.ssh_config or in the ssh_options param (ref: http://net-ssh.github.io/net-ssh/Net/SSH.html#method-c-start)
-      # StorageManager::SFTP.new("www.example.com", base_dir: "/mnt/backup", ssh_options: {})
     end
 
     # Any custom code you want to insert into the default layout without

config/initializers/zeitwerk.rb

@@ -1,5 +1,3 @@
 Rails.autoloaders.each do |autoloader|
-  autoloader.inflector.inflect(
-    "sftp" => "SFTP"
-  )
+  autoloader.inflector.inflect({})
 end