Break retain cycle between view component and observer (#25019)

Summary:
Fixes potential memory leaks.

## Changelog

[iOS] [Fixed] - [Fabric] Break retain cycle between view component and observer
Pull Request resolved: https://github.com/facebook/react-native/pull/25019

Differential Revision: D15499209

Pulled By: shergin

fbshipit-source-id: de53bea5cd5758b9890f3941c39a27d2747bf35b

React/Fabric/RCTImageResponseObserverProxy.h

@@ -24,7 +24,7 @@ namespace facebook {
       void didReceiveFailure() override;
       
     private:
-      id<RCTImageResponseDelegate> delegate_;
+      __weak id<RCTImageResponseDelegate> delegate_;
     };
   }
 }