Update rubocop gem to 0.90.0 (#8313)

Merge pull request 8313

test/helper.rb

@@ -30,7 +30,7 @@ require "minitest/autorun"
 require "minitest/reporters"
 require "minitest/profile"
 require "rspec/mocks"
-require_relative "../lib/jekyll.rb"
+require_relative "../lib/jekyll"
 
 Jekyll.logger = Logger.new(StringIO.new, :error)
 

test/test_tags.rb

@@ -7,7 +7,6 @@ class TestTags < JekyllUnitTest
     FileUtils.mkdir_p("tmp")
   end
 
-  # rubocop:disable Metrics/AbcSize
   def create_post(content, override = {}, converter_class = Jekyll::Converters::Markdown)
     site = fixture_site({ "highlighter" => "rouge" }.merge(override))
 
@@ -23,7 +22,6 @@ class TestTags < JekyllUnitTest
     @result = Liquid::Template.parse(content).render!(payload, info)
     @result = @converter.convert(@result)
   end
-  # rubocop:enable Metrics/AbcSize
 
   def fill_post(code, override = {})
     content = <<~CONTENT