Remove invalidate observer instead of re-adding observer in DeviceInf…

…o module (facebook#43737)

Summary:
Previous fix brings in facebook#42396. Seems it's a mistake to re-add observer?
So let's remove it and also not `invalidate` method not be called twice.

[IOS] [FIXED] - Remove invalidate observer instead of re-adding observer in DeviceInfo module

Pull Request resolved: facebook#43737

Test Plan: Fix for facebook#42120 also works.

Reviewed By: javache

Differential Revision: D55692219

Pulled By: cipolleschi

fbshipit-source-id: dba1ddc39a9f2611fc2b84fadf8c23827891379a

packages/react-native/React/CoreModules/RCTDeviceInfo.mm

@@ -98,6 +98,9 @@ - (void)initialize
 
 - (void)invalidate
 {
+  if (_invalidated) {
+    return;
+  }
   _invalidated = YES;
   [self _cleanupObservers];
 }
@@ -118,10 +121,7 @@ - (void)_cleanupObservers
 
   [[NSNotificationCenter defaultCenter] removeObserver:self name:RCTWindowFrameDidChangeNotification object:nil];
 
-  [[NSNotificationCenter defaultCenter] addObserver:self
-                                           selector:@selector(invalidate)
-                                               name:RCTBridgeWillInvalidateModulesNotification
-                                             object:nil];
+  [[NSNotificationCenter defaultCenter] removeObserver:self name:RCTBridgeWillInvalidateModulesNotification object:nil];
 }
 
 static BOOL RCTIsIPhoneNotched()