[rubygems/rubygems] Don't format executables on `gem update --system`

This restores 3.0 behavior and goes back to not formatting executables
by default on `gem update --system`. This is friendlier for jruby and
doesn't really affect OS packagers.

https://github.com/rubygems/rubygems/commit/1a504b651d

lib/rubygems/commands/setup_command.rb

@@ -15,7 +15,7 @@ class Gem::Commands::SetupCommand < Gem::Command
     require 'tmpdir'
 
     super 'setup', 'Install RubyGems',
-          :format_executable => true, :document => %w[ri],
+          :format_executable => false, :document => %w[ri],
           :force => true,
           :site_or_vendor => 'sitelibdir',
           :destdir => '', :prefix => '', :previous_version => '',