refactor(rubygems): Use schema for fallback API

lib/modules/datasource/rubygems/__fixtures__/rails/info.json

@@ -1 +1 @@
-{"name":"rails","downloads":156058530,"version":"5.2.2","version_downloads":385084,"platform":"ruby","authors":"David Heinemeier Hansson","info":"Ruby on Rails is a full-stack web framework optimized for programmer happiness and sustainable productivity. It encourages beautiful code by favoring convention over configuration.","licenses":["MIT"],"metadata":{},"sha":"d9ff5d9be16ee277dfc8f3c760bf171aa497d8685ec5c8988fba21a3dbd72cd5","project_uri":"https://rubygems.org/gems/rails","gem_uri":"https://rubygems.org/gems/rails-5.2.2.gem","homepage_uri":"http://rubyonrails.org","wiki_uri":"","documentation_uri":"http://api.rubyonrails.org","mailing_list_uri":"http://groups.google.com/group/rubyonrails-talk","source_code_uri":"http://github.com/rails/rails","bug_tracker_uri":"http://github.com/rails/rails/issues","changelog_uri":null,"dependencies":{"development":[],"runtime":[{"name":"actioncable","requirements":"= 5.2.2"},{"name":"actionmailer","requirements":"= 5.2.2"},{"name":"actionpack","requirements":"= 5.2.2"},{"name":"actionview","requirements":"= 5.2.2"},{"name":"activejob","requirements":"= 5.2.2"},{"name":"activemodel","requirements":"= 5.2.2"},{"name":"activerecord","requirements":"= 5.2.2"},{"name":"activestorage","requirements":"= 5.2.2"},{"name":"activesupport","requirements":"= 5.2.2"},{"name":"bundler","requirements":"\u003e= 1.3.0"},{"name":"railties","requirements":"= 5.2.2"},{"name":"sprockets-rails","requirements":"\u003e= 2.0.0"}]}}
+{"name":"rails","downloads":156058530,"version":"5.2.2","version_downloads":385084,"platform":"ruby","authors":"David Heinemeier Hansson","info":"Ruby on Rails is a full-stack web framework optimized for programmer happiness and sustainable productivity. It encourages beautiful code by favoring convention over configuration.","licenses":["MIT"],"metadata":{},"sha":"d9ff5d9be16ee277dfc8f3c760bf171aa497d8685ec5c8988fba21a3dbd72cd5","project_uri":"https://rubygems.org/gems/rails","gem_uri":"https://rubygems.org/gems/rails-5.2.2.gem","homepage_uri":"http://rubyonrails.org","wiki_uri":"","documentation_uri":"http://api.rubyonrails.org","mailing_list_uri":"http://groups.google.com/group/rubyonrails-talk","source_code_uri":"http://github.com/rails/rails","bug_tracker_uri":"http://github.com/rails/rails/issues","changelog_uri":"https://www.railschangelog.com/","dependencies":{"development":[],"runtime":[{"name":"actioncable","requirements":"= 5.2.2"},{"name":"actionmailer","requirements":"= 5.2.2"},{"name":"actionpack","requirements":"= 5.2.2"},{"name":"actionview","requirements":"= 5.2.2"},{"name":"activejob","requirements":"= 5.2.2"},{"name":"activemodel","requirements":"= 5.2.2"},{"name":"activerecord","requirements":"= 5.2.2"},{"name":"activestorage","requirements":"= 5.2.2"},{"name":"activesupport","requirements":"= 5.2.2"},{"name":"bundler","requirements":"\u003e= 1.3.0"},{"name":"railties","requirements":"= 5.2.2"},{"name":"sprockets-rails","requirements":"\u003e= 2.0.0"}]}}