Pend flaky test on truffleruby

Author: eregon

spec/concurrent/edge/erlang_actor_spec.rb

@@ -917,6 +917,8 @@
           end
 
           specify "timing out" do
+            (pending('flaky on truffleruby'); fails) if Concurrent.on_truffleruby?
+
             count_down = Concurrent::CountDownLatch.new
             body = { on_thread: -> { m = receive; count_down.wait; reply m },
                      on_pool:   -> { receive { |m| count_down.wait; reply m } } }