Fix value encoding in json generator controller test update method (#3368)
Fix value encoding in json generator controller test update method (#3368)

Fixes #3367
nshafer/phoenix,michalmuskala/phoenix,0x00evil/phoenix,phoenixframework/phoenix,nshafer/phoenix,rafbgarcia/phoenix,eksperimental/phoenix,optikfluffel/phoenix,michalmuskala/phoenix,keathley/phoenix,jwarwick/phoenix,optikfluffel/phoenix,keathley/phoenix,eksperimental/phoenix,0x00evil/phoenix,phoenixframework/phoenix,nshafer/phoenix,Gazler/phoenix,Gazler/phoenix,rafbgarcia/phoenix,jwarwick/phoenix,rafbgarcia/phoenix,phoenixframework/phoenix,0x00evil/phoenix,optikfluffel/phoenix