Update dependency rdoc to v6.7.0

Author: renovate[bot]

Gemfile

@@ -26,7 +26,7 @@ gemspec
 gem 'minitest', '5.18.1', require: false
 gem 'minitest-hooks', '1.5.0', require: false
 gem 'rake-compiler', '1.2.3', require: false
-gem 'rdoc', '6.1.2.1', require: false
+gem 'rdoc', '6.7.0', require: false
 gem 'rspec-rails', '6.0.3', require: false
 gem 'rubocop', '1.53.1', require: false
 gem 'rubocop-rspec', '2.22.0', require: false