More comments and TODOs

Co-authored-by: Mike McQuaid <mike@mikemcquaid.com>

Library/Homebrew/.rubocop.yml

@@ -18,6 +18,7 @@ Naming/PredicateName:
     - is_64_bit?
 
 # Only enforce documentation for public APIs.
+# Checked by the tests.yml syntax job
 Style/Documentation:
   AllowedConstants:
     - Homebrew

Library/Homebrew/extend/kernel.rb

@@ -2,6 +2,7 @@
 # frozen_string_literal: true
 
 # Contains shorthand Homebrew utility methods like `ohai`, `opoo`, `odisabled`.
+# TODO: move these out of `Kernel`.
 module Kernel
   extend T::Sig