Update rubocop to version 0.59.2

Author: depfu[bot]

Gemfile

@@ -8,7 +8,7 @@ group :test do
     # TODO: Upgrade to >= 0.59 when we drop Rubies below 2.2
     #     Error: Unsupported Ruby version 2.1 found in `TargetRubyVersion` parameter (in .rubocop.yml). 2.1-compatible analysis was dropped after version 0.58.
     #     Supported versions: 2.2, 2.3, 2.4, 2.5
-    gem 'rubocop', '~> 0.58.0'
+    gem 'rubocop', '~> 0.59.2'
     gem 'rubocop-rspec', '~> 1.30.0'
   end
   gem 'pry', '~> 0.11' if ruby_version >= Gem::Version.new('2.0')