Simplify rendering a banner

Now the banner component accepts either a banner or a section and loads
the banner if it's a section, so we don't have to add the `@banners`
variable in several controllers.

app/controllers/budgets_controller.rb

@@ -17,7 +17,6 @@ class BudgetsController < ApplicationController
   def index
     @finished_budgets = @budgets.finished.order(created_at: :desc)
     @budgets_coordinates = current_budget_map_locations
-    @banners = Banner.in_section("budgets").with_active
   end
 
   private