Fix GUIDE.md
Fix GUIDE.md

* Fix markdown on code block
k0kubun/byebug,icebreaker/byebug,yui-knk/byebug,yui-knk/byebug,guilherme/byebug,yui-knk/byebug,k0kubun/byebug,ozydingo/byebug,os97673/byebug,deivid-rodriguez/byebug,ozydingo/byebug,deivid-rodriguez/byebug,k0kubun/byebug,deivid-rodriguez/byebug,scalp42/byebug,miamiruby/byebug,saisai/byebug,miamiruby/byebug,icebreaker/byebug,guilherme/byebug,webdev1001/byebug,webdev1001/byebug,saisai/byebug,os97673/byebug,guilherme/byebug,scalp42/byebug