[rubygems/rubygems] Don't hide original error in after(:suite) hook

For some reason, Windows builds are failing quite consistently now.
However, it seems that errors are happening before this directory is
even created, so removal fails, hiding the original error.

Instead, don't let this removal fail due to files not existing.

7669d6c96e

spec/bundler/spec_helper.rb

@@ -114,6 +114,6 @@ RSpec.configure do |config|
   end
 
   config.after :suite do
-    FileUtils.rm_r Spec::Path.pristine_system_gem_path
+    FileUtils.rm_rf Spec::Path.pristine_system_gem_path
   end
 end