(maint) - update litmus pin

Author: jordanbreen28

Gemfile

@@ -37,7 +37,7 @@ group :development do
   gem "github_changelog_generator", '= 1.15.2',        require: false
 end
 group :system_tests do
-  gem "puppet_litmus", '<= 0.34.6', require: false, platforms: [:ruby]
+  gem "puppet_litmus", '~> 1.0',   require: false, platforms: [:ruby]
   gem "serverspec", '~> 2.41',      require: false
 end