Pin rubocop version (#8564)
Pin rubocop version (#8564)

Merge pull request 8564
x-way/jekyll,jekyll/jekyll,fulldecent/jekyll,x-way/jekyll,chrisfinazzo/jekyll,jekyll/jekyll,x-way/jekyll,jaybe-jekyll/jekyll,jekyll/jekyll,ryanshaw/jekyll,fulldecent/jekyll,fulldecent/jekyll,fulldecent/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll,chrisfinazzo/jekyll,x-way/jekyll,jaybe-jekyll/jekyll,jaybe-jekyll/jekyll,ryanshaw/jekyll,jekyll/jekyll,ryanshaw/jekyll,chrisfinazzo/jekyll