Remove unneeded namespace methods

These methods are not necessary since we changed the `namespace` helper
method in commit 13b3d9ceb.

app/controllers/officing/ballot_sheets_controller.rb

@@ -3,8 +3,6 @@ class Officing::BallotSheetsController < Officing::BaseController
   before_action :load_poll
   before_action :load_officer_assignments, only: [:new, :create]
 
-  helper_method :namespace
-
   def index
     load_ballot_sheets
   end
@@ -31,10 +29,6 @@ class Officing::BallotSheetsController < Officing::BaseController
 
   private
 
-    def namespace
-      "officing"
-    end
-
     def load_poll
       @poll = Poll.find(params[:poll_id])
     end