Add missing divider in upgrading-guide [skip ci]
Add missing divider in upgrading-guide [skip ci]

tillgrallert/jekyll,fulldecent/jekyll,Strangehill/jekyll,tillgrallert/jekyll,tillgrallert/jekyll,Strangehill/jekyll,ryanshaw/jekyll,jekyll/jekyll,x-way/jekyll,jekyll/jekyll,Strangehill/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,jekyll/jekyll,yhironaka/yhironaka.github.io,fulldecent/jekyll,x-way/jekyll,x-way/jekyll,jaybe-jekyll/jekyll,x-way/jekyll,Strangehill/jekyll,jaybe-jekyll/jekyll,fulldecent/jekyll,tillgrallert/jekyll,ryanshaw/jekyll,fulldecent/jekyll,chrisfinazzo/jekyll,chrisfinazzo/jekyll,chrisfinazzo/jekyll,jekyll/jekyll,ryanshaw/jekyll,Strangehill/jekyll,tillgrallert/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll