cmd/link: don't link shadowed macOS software.

Library/Homebrew/cmd/link.rb

@@ -68,10 +68,10 @@ module Homebrew
       if keg_only
         if Homebrew.default_prefix?
           f = keg.to_formula
-          if f.keg_only_reason.reason == :provided_by_macos
+          if f.keg_only_reason.reason.by_macos?
             caveats = Caveats.new(f)
             opoo <<~EOS
-              Refusing to link macOS-provided software: #{keg.name}
+              Refusing to link macOS provided/shadowed software: #{keg.name}
               #{caveats.keg_only_text(skip_reason: true).strip}
             EOS
             next