Bump RuboCop to 0.68.1

Performance cops were extracted in rubocop/rubocop#5977 and @koic
updated to 0.67.2 and added the rubocop-performance gem in rails#35989.

This bumps rubocop to 0.68.1 to be on the latest version. Two changes
were made in regards to the bump of the version:
* The first was that Layout/FirstParameterIndentation was renamed to
Layout/IndentFirstArgument. These changes can be seen in
rubocop/rubocop#6982 and rubocop/rubocop#6987
* The second was that a new instance of the Style/HashSyntax cop was
found. I updated that instance to follow the new Ruby >= 1.9 syntax.

.rubocop.yml

@@ -77,7 +77,7 @@ Layout/EmptyLinesAroundMethodBody:
 Layout/EmptyLinesAroundModuleBody:
   Enabled: true
 
-Layout/FirstParameterIndentation:
+Layout/IndentFirstArgument:
   Enabled: true
 
 # Use Ruby >= 1.9 syntax for hashes. Prefer { a: :b } over { :a => :b }.

Gemfile.lock

@@ -411,11 +411,10 @@ GEM
       resque (~> 1.26)
       rufus-scheduler (~> 3.2)
     retriable (3.1.2)
-    rubocop (0.67.2)
+    rubocop (0.68.1)
       jaro_winkler (~> 1.5.1)
       parallel (~> 1.10)
       parser (>= 2.5, != 2.5.1.1)
-      psych (>= 3.1.0)
       rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 1.4.0, < 1.6)

actionview/test/actionpack/abstract/layouts_test.rb

@@ -295,7 +295,7 @@ class TestBase < ActiveSupport::TestCase
         10.times do |x|
           controller = WithString.new
           controller.define_singleton_method :index do
-            render template: ActionView::Template::Text.new("Hello string!"), locals: { :"x#{x}" => :omg }
+            render template: ActionView::Template::Text.new("Hello string!"), locals: { "x#{x}": :omg }
           end
           controller.process(:index)
         end