Update "Requirements" for Ruby version (#6623)
Update "Requirements" for Ruby version (#6623)

Merge pull request 6623
jaybe-jekyll/jekyll,getandpost/jekyll.github.io,jaybe-jekyll/jekyll,Strangehill/jekyll,gencer/jekyll,x-way/jekyll,yhironaka/yhironaka.github.io,ryanshaw/jekyll,x-way/jekyll,Strangehill/jekyll,jekyll/jekyll,jaybe-jekyll/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,fulldecent/jekyll,jekyll/jekyll,chrisfinazzo/jekyll,gencer/jekyll,Strangehill/jekyll,getandpost/jekyll.github.io,jekyll/jekyll,tillgrallert/jekyll,x-way/jekyll,ryanshaw/jekyll,tillgrallert/jekyll,gencer/jekyll,gencer/jekyll,fulldecent/jekyll,tillgrallert/jekyll,Strangehill/jekyll,fulldecent/jekyll,gencer/jekyll,getandpost/jekyll.github.io,fulldecent/jekyll,x-way/jekyll,chrisfinazzo/jekyll,chrisfinazzo/jekyll,tillgrallert/jekyll,Strangehill/jekyll,chrisfinazzo/jekyll,jekyll/jekyll,tillgrallert/jekyll,ryanshaw/jekyll