Use JSON.parse in AP inboxes (#38238)

app/controllers/activitypub/inboxes_controller.rb

@@ -26,9 +26,9 @@ class ActivityPub::InboxesController < ActivityPub::BaseController
   end
 
   def unknown_affected_account?
-    json = Oj.load(body, mode: :strict)
+    json = JSON.parse(body)
     json.is_a?(Hash) && %w(Delete Update).include?(json['type']) && json['actor'].present? && json['actor'] == value_or_id(json['object']) && !Account.exists?(uri: json['actor'])
-  rescue Oj::ParseError
+  rescue JSON::ParserError
     false
   end