Fixed buggy Observable shared spec.

Author: jdantonio

spec/concurrent/observable_shared.rb

@@ -125,6 +125,7 @@ def notify(*args)
         subject.add_observer(observer_class.new{ latch.count_down })
       end
       trigger_observable(subject)
+      latch.wait(1)
       expect(latch.count).to eq 0
     end