Fix a bug in ObserverManager destructor

Summary: facepaw

Reviewed By: ckwalsh

Differential Revision: D3853363

fbshipit-source-id: f863a3e3ae830256f5cff6c56f23254ff6fdee2a

folly/experimental/observer/detail/ObserverManager.cpp

@@ -147,8 +147,8 @@ ObserverManager::ObserverManager() {
 ObserverManager::~ObserverManager() {
   // Destroy NextQueue, before the rest of this object, since it expects
   // ObserverManager to be alive.
-  nextQueue_.release();
-  currentQueue_.release();
+  nextQueue_.reset();
+  currentQueue_.reset();
 }
 
 void ObserverManager::scheduleCurrent(Function<void()> task) {