[rubygems/rubygems] Exclude truffleruby from the test for failure of operating_system.rb

truffleruby does not raise any error when requiring `rubygems`.

https://github.com/rubygems/rubygems/commit/21e2fcd0b2

test/rubygems/test_rubygems.rb

@@ -7,6 +7,8 @@ class GemTest < Gem::TestCase
   end
 
   def test_operating_system_other_exceptions
+    pend "does not apply to truffleruby" if RUBY_ENGINE == 'truffleruby'
+
     path = util_install_operating_system_rb <<-RUBY
       intentional synt'ax error
     RUBY