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

spec/components/admin/budget_headings/form_component_spec.rb

@@ -26,7 +26,8 @@ describe Admin::BudgetHeadings::FormComponent do
 
       render_inline component
 
-      expect(page).to have_select "Scope of operation", options: ["All city", "Under the sea", "Above the skies"]
+      expect(page).to have_select "Scope of operation",
+                                  options: ["All city", "Under the sea", "Above the skies"]
     end
   end
 end