 Fix rollback/2 in releases guide (#3489)
 Fix rollback/2 in releases guide (#3489)

* Load application before attempting rollback

* Update releases.md

phoenixframework/phoenix,jwarwick/phoenix,Gazler/phoenix,optikfluffel/phoenix,jwarwick/phoenix,michalmuskala/phoenix,phoenixframework/phoenix,rafbgarcia/phoenix,0x00evil/phoenix,keathley/phoenix,michalmuskala/phoenix,keathley/phoenix,nshafer/phoenix,0x00evil/phoenix,0x00evil/phoenix,eksperimental/phoenix,rafbgarcia/phoenix,optikfluffel/phoenix,optikfluffel/phoenix,nshafer/phoenix,Gazler/phoenix,nshafer/phoenix,eksperimental/phoenix,phoenixframework/phoenix,rafbgarcia/phoenix