add bounded gem dependencies for target versions >= ruby2.7

puppet-ghostbuster.gemspec

@@ -13,15 +13,15 @@ Gem::Specification.new do |s|
   s.files       = `git ls-files`.split("\n")
   s.executables = `git ls-files -- bin/*`.split("\n").map { |f| File.basename(f) }
 
-  s.add_development_dependency 'coveralls'
-  s.add_development_dependency 'github_changelog_generator'
-  s.add_development_dependency 'jgrep'
-  s.add_development_dependency 'rake'
+  s.add_development_dependency 'coveralls', '>= 0.8', '< 0.9'
+  s.add_development_dependency 'github_changelog_generator', '>= 1.16.0', '< 1.17.0'
+  s.add_development_dependency 'jgrep', '>= 1.0.0', '< 2.0.0'
+  s.add_development_dependency 'rake', '>= 13.0.0', '< 14.0.0'
   s.add_development_dependency 'rspec', '~> 3.0'
   s.add_development_dependency 'rspec-collection_matchers', '~> 1.0'
   s.add_development_dependency 'rspec-its', '~> 1.0'
-  s.add_runtime_dependency 'json'
-  s.add_runtime_dependency 'puppet'
+  s.add_runtime_dependency 'json', '>= 2.0', '< 3.0'
+  s.add_runtime_dependency 'puppet', '>= 6.0', '< 9.0'
   s.add_dependency         'puppet-lint', '>= 1.0', '< 3.0'
   s.add_runtime_dependency 'puppetdb-ruby', '~> 1.1', '>= 1.1.1'
 end