Fix race condition in Binding::reportMount (facebook#39420)

Summary:
Pull Request resolved: facebook#39420

changelog: [internal]

The intent of the code is to retain shared_ptr<Scheduler> but by using a reference, it didn't do that. Leading to a race condition.

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Reviewed By: rubennorte

Differential Revision: D49227147

fbshipit-source-id: 1a548f7174eacb95c14c89f72b51ccd263c5ab01

packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.cpp

@@ -98,7 +98,7 @@ void Binding::driveCxxAnimations() {
 }
 
 void Binding::reportMount(SurfaceId surfaceId) {
-  const auto& scheduler = getScheduler();
+  auto scheduler = getScheduler();
   if (!scheduler) {
     LOG(ERROR) << "Binding::reportMount: scheduler disappeared";
     return;