rubocops/cask: Clean up unnecessary requires

- I suspect these were copy-pasted from other cops, like I did in
  Homebrew#14886 (comment).
- The "forwardable" require is unnecesary if the cop doesn't
  `extend Forwardable` and use `def_delegator`.
- The "uri" require is unnecessary if the cop doesn't call `URI` methods.

Library/Homebrew/rubocops/cask/desc.rb

@@ -1,8 +1,6 @@
 # typed: true
 # frozen_string_literal: true
 
-require "forwardable"
-require "uri"
 require "rubocops/cask/mixin/on_desc_stanza"
 require "rubocops/shared/desc_helper"
 

Library/Homebrew/rubocops/cask/url_legacy_comma_separators.rb

@@ -1,9 +1,6 @@
 # typed: true
 # frozen_string_literal: true
 
-require "forwardable"
-require "uri"
-
 module RuboCop
   module Cop
     module Cask