rubocops/cask: Appease Sorbet with the correct inheritance

- The `on_url_stanza` method is now used in two cops, `Url` and
  `UrlLegacyCommaSeparators`. Make the latter inherit from the former
  to make Sorbet happy.
- The style and typecheck checks now pass fine.

Library/Homebrew/rubocops/cask/mixin/on_url_stanza.rbi

@@ -1,5 +1,5 @@
 # typed: strict
 
 module RuboCop::Cop::Cask::OnUrlStanza
-  requires_ancestor { RuboCop::Cop::Cask::UrlLegacyCommaSeparators }
+  requires_ancestor { RuboCop::Cop::Cask::Url }
 end

Library/Homebrew/rubocops/cask/url_legacy_comma_separators.rb

@@ -8,7 +8,7 @@ module RuboCop
   module Cop
     module Cask
       # This cop checks for version.before_comma and version.after_comma
-      class UrlLegacyCommaSeparators < Base
+      class UrlLegacyCommaSeparators < Url
         include OnUrlStanza
         extend AutoCorrector