Update puppet_metadata requirement from ~> 3.5 to ~> 4.0

Updates the requirements on [puppet_metadata](https://github.com/voxpupuli/puppet_metadata) to permit the latest version.
- [Changelog](https://github.com/voxpupuli/puppet_metadata/blob/master/CHANGELOG.md)
- [Commits](voxpupuli/puppet_metadata@3.5.0...4.0.0)

---
updated-dependencies:
- dependency-name: puppet_metadata
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile

@@ -7,7 +7,7 @@ group :test do
   gem 'voxpupuli-test', '~> 7.0',   :require => false
   gem 'coveralls',                  :require => false
   gem 'simplecov-console',          :require => false
-  gem 'puppet_metadata', '~> 3.5',  :require => false
+  gem 'puppet_metadata', '~> 4.0',  :require => false
 end
 
 group :development do