style: fix tap checking

`brew style` tap support was broken in 7d0ac4d (#17357), so now
something like `brew style homebrew/core` exits without checking
anything. This happens because the new file-handling logic doesn't
do anything with a tap path. Previously, a tap path would be added
to `ruby_files` but now it isn't added to any of the arrays of files
to check.

This fixes the issue by adding some logic to add the path to the
`ruby_files` array if it's a tap.

Library/Homebrew/style.rb

@@ -57,6 +57,7 @@ module Homebrew
         when ".yml"
           actionlint_files << path if path.realpath.to_s.include?("/.github/workflows/")
         else
+          ruby_files << path if path.tap?
           shell_files << path if path.realpath == HOMEBREW_BREW_FILE.realpath
         end
       end