Update  error messages of Phoenix.Channel.Server (#3008)
Update  error messages of Phoenix.Channel.Server (#3008)

* Format error in Phoenix.Channel.Server

* Remove backticks from error messages

0x00evil/phoenix,optikfluffel/phoenix,Kosmas/phoenix,phoenixframework/phoenix,Kosmas/phoenix,keathley/phoenix,Joe-noh/phoenix,pap/phoenix,nshafer/phoenix,michalmuskala/phoenix,phoenixframework/phoenix,Gazler/phoenix,keathley/phoenix,jwarwick/phoenix,Gazler/phoenix,optikfluffel/phoenix,nshafer/phoenix,jwarwick/phoenix,eksperimental/phoenix,evax/phoenix,eksperimental/phoenix,rafbgarcia/phoenix,evax/phoenix,nshafer/phoenix,phoenixframework/phoenix,Joe-noh/phoenix,0x00evil/phoenix,dmarkow/phoenix,mitchellhenke/phoenix,0x00evil/phoenix,mschae/phoenix,rafbgarcia/phoenix,pap/phoenix,optikfluffel/phoenix,mschae/phoenix,michalmuskala/phoenix,mitchellhenke/phoenix,rafbgarcia/phoenix,dmarkow/phoenix