Apply Style/SymbolProc rubocop rule

This style is much more concise.

app/controllers/admin/site_customization/content_blocks_controller.rb

@@ -9,7 +9,7 @@ class Admin::SiteCustomization::ContentBlocksController < Admin::SiteCustomizati
   def index
     @content_blocks = SiteCustomization::ContentBlock.order(:name, :locale)
     @headings_content_blocks = Budget::ContentBlock.all
-    all_settings = Setting.all.group_by { |setting| setting.type }
+    all_settings = Setting.all.group_by(&:type)
     @html_settings = all_settings["html"]
   end