Update puppetlabs_spec_helper requirement from ~> 7.0 to ~> 8.0

Updates the requirements on [puppetlabs_spec_helper](https://github.com/puppetlabs/puppetlabs_spec_helper) to permit the latest version.
- [Release notes](https://github.com/puppetlabs/puppetlabs_spec_helper/releases)
- [Changelog](https://github.com/puppetlabs/puppetlabs_spec_helper/blob/main/CHANGELOG.md)
- [Commits](puppetlabs/puppetlabs_spec_helper@v7.0.0...v8.0.0)

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

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

Gemfile

@@ -5,7 +5,7 @@ group :development, :test do
   gem 'rspec', '~> 3.5'
   gem 'rspec-puppet', '~> 5.0'
   gem 'pdk', '~> 3.0'
-  gem 'puppetlabs_spec_helper', '~> 7.0'
+  gem 'puppetlabs_spec_helper', '~> 8.0'
   gem 'puppet-blacksmith', '~> 6.1'
   gem 'puppet-lint', '~> 4.0'
   gem 'metadata-json-lint', '~> 4.0'