fix(bin/kitchen): fix rubocop errors

ssf/files/default/bin/kitchen

@@ -8,22 +8,25 @@
 # this file is here to facilitate running it.
 #
 
-require "pathname"
-ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
-  Pathname.new(__FILE__).realpath)
+require 'pathname'
+ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile',
+                                           Pathname.new(__FILE__).realpath)
 
-bundle_binstub = File.expand_path("../bundle", __FILE__)
+bundle_binstub = File.expand_path('bundle', __dir__)
 
 if File.file?(bundle_binstub)
   if File.read(bundle_binstub, 300) =~ /This file was generated by Bundler/
     load(bundle_binstub)
   else
-    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
-Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+    abort(
+      'Your `bin/bundle` was not generated by Bundler, '\
+      'so this binstub cannot run.  Replace `bin/bundle` by running '\
+      '`bundle binstubs bundler --force`, then run this command again.'
+    )
   end
 end
 
-require "rubygems"
-require "bundler/setup"
+require 'rubygems'
+require 'bundler/setup'
 
-load Gem.bin_path("test-kitchen", "kitchen")
+load Gem.bin_path('test-kitchen', 'kitchen')