only remove weak instance

packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/instance_manager.dart

@@ -117,7 +117,6 @@ class InstanceManager {
   /// This does not remove the the weak referenced instance associtated with
   /// [identifier]. This can be done with [removeWeakReference].
   T? remove<T extends Copyable>(int identifier) {
-    _weakInstances.remove(identifier);
     return _strongInstances.remove(identifier) as T?;
   }
 

packages/webview_flutter/webview_flutter_wkwebview/test/src/foundation/foundation_test.dart

@@ -154,6 +154,7 @@ void main() {
         object = NSObject(instanceManager: instanceManager);
         instanceManager.addHostCreatedInstance(object, 1);
 
+        instanceManager.removeWeakReference(object);
         FoundationFlutterApis.instance.object.dispose(1);
 
         expect(instanceManager.containsIdentifier(1), isFalse);