GithubHelper: Fix Rubocop Issues

Author: raafaelima

lib/fastlane/plugin/wpmreleasetoolkit/helper/github_helper.rb

@@ -80,8 +80,8 @@ def get_last_milestone(repository)
       # @param [Integer] days_until_release Number of days from code freeze to release
       #
       def create_milestone(repository:, title:, due_date:, days_until_submission:, days_until_release:)
-        UI.user_error!('days_until_release must be greater than zero.') unless days_until_release > 0
-        UI.user_error!('days_until_submission must be greater than zero.') unless days_until_submission > 0
+        UI.user_error!('days_until_release must be greater than zero.') unless days_until_release.positive?
+        UI.user_error!('days_until_submission must be greater than zero.') unless days_until_submission.positive?
         UI.user_error!('days_until_release must be greater or equal to days_until_submission.') unless days_until_release >= days_until_submission
 
         submission_date = due_date.to_datetime.next_day(days_until_submission)