Add override to RCTHermesInstance destructor (facebook#48265)

Summary:
Pull Request resolved: facebook#48265

For some clang warnings configurations, you may hit `-Winconsistent-missing-destructor-override` without this override modifier.

## Changelog

[Internal]

Reviewed By: cipolleschi

Differential Revision: D67203040

fbshipit-source-id: 51f8f9bc4e45ebdb008dc440b779302b1103668a

Author: rozele

Diff for: packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTHermesInstance.h

@@ -30,7 +30,7 @@ class RCTHermesInstance : public JSRuntimeFactory {
   std::unique_ptr<JSRuntime> createJSRuntime(
       std::shared_ptr<MessageQueueThread> msgQueueThread) noexcept override;
 
-  ~RCTHermesInstance(){};
+  ~RCTHermesInstance() override{};
 
  private:
   CrashManagerProvider _crashManagerProvider;