Remove setting for unfollow confirmation modal, and make it unconditional (#29373)

app/models/concerns/user/has_settings.rb

@@ -27,10 +27,6 @@ module User::HasSettings
     settings['default_sensitive']
   end
 
-  def setting_unfollow_modal
-    settings['web.unfollow_modal']
-  end
-
   def setting_boost_modal
     settings['web.reblog_modal']
   end

app/models/user_settings.rb

@@ -27,7 +27,6 @@ class UserSettings
     setting :disable_swiping, default: false
     setting :delete_modal, default: true
     setting :reblog_modal, default: false
-    setting :unfollow_modal, default: true
     setting :reduce_motion, default: false
     setting :expand_content_warnings, default: false
     setting :display_media, default: 'default', in: %w(default show_all hide_all)