DEV: Leaking state in PostActionNotifier in tests take 2.

Follow-up to a3b48826

spec/services/post_action_notifier_spec.rb

@@ -108,6 +108,10 @@ describe PostActionNotifier do
         end
       end
 
+      after do
+        PostActionNotifier.reset!
+      end
+
       it 'notifies the specified user of the revision' do
         expect {
           post.revise(evil_trout, raw: "world is the new body of the message")