Add missing faraday dep

This is an optional dependency for gcg. but we get an annoying warning
if it's missing.

Gemfile

@@ -20,6 +20,7 @@ group :acceptance_testing do
   gem 'beaker', *location_for(ENV.fetch('BEAKER_VERSION', '~> 4.0'))
 end
 
-group :release do
-  gem 'github_changelog_generator', require: false
+group :release, optional: true do
+  gem 'faraday-retry', '~> 2.1', require: false
+  gem 'github_changelog_generator', '~> 1.16.4', require: false
 end