Require Parser 2.7.0.1 or higher

Follow up of #7606 (comment).

Parser 2.7.0.0 has the following issue.
#7597

This PR changes to require Parser gem 2.7.0.1 or higher.
Parser 2.7 is compatible with Parser 2.6, so I think it's safe
to upgrade.

rubocop.gemspec

@@ -35,7 +35,7 @@ Gem::Specification.new do |s|
 
   s.add_runtime_dependency('jaro_winkler', '~> 1.5.1')
   s.add_runtime_dependency('parallel', '~> 1.10')
-  s.add_runtime_dependency('parser', '>= 2.6')
+  s.add_runtime_dependency('parser', '>= 2.7.0.1')
   s.add_runtime_dependency('rainbow', '>= 2.2.2', '< 4.0')
   s.add_runtime_dependency('ruby-progressbar', '~> 1.7')
   s.add_runtime_dependency('unicode-display_width', '>= 1.4.0', '< 1.7')