Fix clang warning for -Winconsistent-missing-destructor-override (#42942

)

Summary:
Pull Request resolved: #42942

Instance derives from jsinspector_modern::InstanceTargetDelegate, which defines a virtual destructor, but Instance does not mark its destructor with override.

## Changelog [Internal]

Reviewed By: cipolleschi

Differential Revision: D53609922

fbshipit-source-id: b30df7d59478fa72b53ddc2eeb04c291a6f5f9eb

packages/react-native/ReactCommon/cxxreact/Instance.h

@@ -41,7 +41,7 @@ struct InstanceCallback {
 
 class RN_EXPORT Instance : private jsinspector_modern::InstanceTargetDelegate {
  public:
-  ~Instance();
+  ~Instance() override;
   void initializeBridge(
       std::unique_ptr<InstanceCallback> callback,
       std::shared_ptr<JSExecutorFactory> jsef,