(CAT-2281) Remove puppet 7 infrastructure

Puppet 7 is EOL. Therefore, we can remove the test infrastructure for it.
This commit aims to clear up any testing/config infrastructure related to
Puppet 7 and, by extension, Ruby 2.7.

Author: LukasAud

.rubocop.yml

@@ -4,7 +4,7 @@ require:
 - rubocop-rspec
 AllCops:
   DisplayCopNames: true
-  TargetRubyVersion: '2.7'
+  TargetRubyVersion: '3.1'
   SuggestExtensions: false
   Include:
   - "**/*.rb"

puppet-lint-check_unsafe_interpolations.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   EOF
   spec.homepage      = 'https://github.com/puppetlabs/puppet-lint-check_unsafe_interpolations'
   spec.license       = 'Apache-2.0'
-  spec.required_ruby_version = Gem::Requirement.new(">= 2.5".freeze)
+  spec.required_ruby_version = Gem::Requirement.new(">= 3.1".freeze)
 
   spec.add_dependency 'puppet-lint', '~> 4.0'
 end