Apply Layout/LineLength rubocop rule

Note we're excluding a few files:

* Configuration files that weren't generated by us
* Migration files that weren't generated by us
* The Gemfile, since it includes an important comment that must be on
  the same line as the gem declaration
* The Budget::Stats class, since the heading statistics are a mess and
  having shorter lines would require a lot of refactoring

app/controllers/admin/api/stats_controller.rb

@@ -22,7 +22,8 @@ class Admin::Api::StatsController < Admin::Api::BaseController
     end
 
     if params[:user_supported_budgets].present?
-      ds.add "User supported budgets", Vote.where(votable_type: "Budget::Investment").group_by_day(:updated_at).count
+      ds.add "User supported budgets",
+             Vote.where(votable_type: "Budget::Investment").group_by_day(:updated_at).count
     end
     render json: ds.build
   end