chore(deps): update dependency github_changelog_generator to '~> 1.18.0'

Author: renovate[bot]

Gemfile

@@ -7,5 +7,5 @@ source ENV['GEM_SOURCE'] || 'https://rubygems.org'
 
 group :release do
   gem 'faraday-retry', '~> 2.1', require: false
-  gem 'github_changelog_generator', '~> 1.17.0', require: false
+  gem 'github_changelog_generator', '~> 1.18.0', require: false
 end