Do not require programs languages in controller

We did not set this in ProposalController#create so it was empty
if we the event validation failed and we rendered :new.

It makes little sense to assign this instance variable anyway, we already have
@program.

app/controllers/proposals_controller.rb

@@ -23,12 +23,10 @@ class ProposalsController < ApplicationController
   def new
     @user = User.new
     @url = conference_program_proposals_path(@conference.short_title)
-    @languages = @program.languages_list
   end
 
   def edit
     @url = conference_program_proposal_path(@conference.short_title, params[:id])
-    @languages = @program.languages_list
   end
 
   def create