remove litmus gem

Author: MartyEwings

.sync.yml

@@ -57,7 +57,3 @@ Gemfile:
   optional:
     ":development":
     - gem: github_changelog_generator
-    - gem: puppet_litmus
-      git: https://github.com/puppetlabs/puppet_litmus
-      ref: main
-      condition: Gem::Version.new(RUBY_VERSION.dup) >= Gem::Version.new('2.5.0')