Rails/DeprecatedActiveModelErrorsMethods detected even though Rails 6.0

[obregonia1]

https://apidock.com/rails/v6.1.3.1/ActiveModel/Errors/attribute_names
Rails/DeprecatedActiveModelErrorsMethods detected Rails 6.0 app but ActiveModel::Errors#attribute_names was added in Rails 6.1.3.1.

# Gemfile.lock
 rails (6.0.5)

---

Expected behavior

Rails/DeprecatedActiveModelErrorsMethods doesn't detected in Rails 6.0.

Actual behavior

Rails/DeprecatedActiveModelErrorsMethods detected in Rails 6.0.

Steps to reproduce the problem

user.errors.keys.include?(:attr)

RuboCop version

bundle exec rubocop -V
1.31.0 (using Parser 3.1.2.0, rubocop-ast 1.18.0, running on ruby 2.7.6 aarch64-linux-musl)
  - rubocop-rails 2.15.1
  - rubocop-rspec 2.11.1