Add more tests for ActivityPub controllers (#13585)

app/controllers/api/v1/statuses/mutes_controller.rb

@@ -28,8 +28,7 @@ class Api::V1::Statuses::MutesController < Api::BaseController
     @status = Status.find(params[:status_id])
     authorize @status, :show?
   rescue Mastodon::NotPermittedError
-    # Reraise in order to get a 404 instead of a 403 error code
-    raise ActiveRecord::RecordNotFound
+    not_found
   end
 
   def set_conversation