Update dependency rdoc to v6.13.0

Author: renovate[bot]

Gemfile

@@ -9,7 +9,7 @@ gemspec
 gem 'minitest', '~>5.18', require: false
 gem 'minitest-hooks', '~>1.5', require: false
 gem 'rake-compiler', '~>1.2', require: false
-gem 'rdoc', '6.1.2.1', require: false
+gem 'rdoc', '6.13.0', require: false
 gem 'rspec-rails', '~>6.0', require: false
 gem 'rubocop', '~>1.53', require: false
 gem 'rubocop-minitest', '>0', require: false