cmd/setup-ruby: use ShellCommand

Library/Homebrew/cmd/setup-ruby.rb

@@ -2,10 +2,13 @@
 # frozen_string_literal: true
 
 require "abstract_command"
+require "shell_command"
 
 module Homebrew
   module Cmd
     class SetupRuby < AbstractCommand
+      include ShellCommand
+
       cmd_args do
         description <<~EOS
           Installs and configures Homebrew's Ruby. If `command` is passed, it will only run Bundler if necessary for that command.
@@ -13,9 +16,6 @@ module Homebrew
 
         named_args :command
       end
-
-      sig { override.void }
-      def run = raise_sh_command_error!
     end
   end
 end