Add preference setting for delete toot modal (#3368)

* Set delete_modal preference to true by default
* Does not show confirmation modal if delete_modal is false
* Add ja translation for preference setting page

app/models/user.rb

@@ -80,6 +80,10 @@ class User < ApplicationRecord
     settings.boost_modal
   end
 
+  def setting_delete_modal
+    settings.delete_modal
+  end
+
   def setting_auto_play_gif
     settings.auto_play_gif
   end