Update r10k requirement from ~> 3.15 to ~> 4.0

Updates the requirements on [r10k](https://github.com/puppetlabs/r10k) to permit the latest version.
- [Changelog](https://github.com/puppetlabs/r10k/blob/main/CHANGELOG.mkd)
- [Commits](puppetlabs/r10k@3.15.0...4.0.0)

---
updated-dependencies:
- dependency-name: r10k
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile

@@ -5,7 +5,7 @@ gem 'onceover-codequality',          '~> 0.10'
 gem 'onceover-lookup',               '~> 0.1', '>= 0.1.1'
 gem 'onceover-octocatalog-diff',     '~> 0.1', '>= 0.1.8'
 gem 'onceover',                      '~> 3.20'
-gem 'r10k',                          '~> 3.15'
+gem 'r10k',                          '~> 4.0'
 gem 'ra10ke',                        '~> 2.0'
 gem 'voxpupuli-acceptance',          '~> 2.1'
 gem 'voxpupuli-test',                '~> 6.0'