Require Ruby 3.1

Ruby 3.0 and older are dead upstream. Requiring 3.1 or newer allows us
to safely use latest gem dependencies. Beaker isn't tied to the Puppet
AIO Ruby versions, so we don't need to stay on Ruby 2.6 or 2.7.

.rubocop.yml

@@ -4,6 +4,9 @@ inherit_from: .rubocop_todo.yml
 inherit_gem:
   voxpupuli-rubocop: rubocop.yml
 
+AllCops:
+  TargetRubyVersion: 3.1
+
 Layout/LineLength:
   Exclude:
     - acceptance/**/*.rb

beaker.gemspec

@@ -16,7 +16,7 @@ Gem::Specification.new do |s|
   s.executables   = `git ls-files -- bin/*`.split("\n").map { |f| File.basename(f) }
   s.require_paths = ["lib"]
 
-  s.required_ruby_version = Gem::Requirement.new('>= 2.7')
+  s.required_ruby_version = Gem::Requirement.new('>= 3.1')
 
   # Testing dependencies
   s.add_development_dependency 'fakefs', '~> 2.4'
@@ -25,7 +25,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'voxpupuli-rubocop', '~> 2.8.0'
 
   # Run time dependencies
-  s.add_runtime_dependency 'minitar', '~> 0.12' # newer versions require Ruby 3.1
+  s.add_runtime_dependency 'minitar', '>= 0.12', '< 2'
   s.add_runtime_dependency 'minitest', '~> 5.4'
   s.add_runtime_dependency 'rexml', '~> 3.2', '>= 3.2.5'