Keep ES6Proxy enabled in bridgeless mode (facebook#43538)

Summary:
Pull Request resolved: facebook#43538

The Hermes RuntimeConfig for bridgeless accidentally force-disabled ES6Proxy, resulting in facebook#43523

Let's remove the incorrect override.

To test using RNTester, add the following change:

```
 diff --git a/packages/rn-tester/js/RNTesterAppShared.js b/packages/rn-tester/js/RNTesterAppShared.js
index 87cb6b69dfe..f2512d09c5a 100644
 --- a/packages/rn-tester/js/RNTesterAppShared.js
+++ b/packages/rn-tester/js/RNTesterAppShared.js
@@ -50,6 +50,8 @@ const RNTesterApp = ({
   );
   const colorScheme = useColorScheme();
+  new Proxy({}, {});
+
   const {
     activeModuleKey,
     activeModuleTitle,
```

Before this change, RNTester will get an error at start-up. After, the app loads correctly.

Changelog: [General][Fixed] Correctly keep ES6Proxy for bridgeless mode

Reviewed By: cortinico

Differential Revision: D55045780

fbshipit-source-id: 666b99712d35622f87d42f22a4611851df67d905

packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp

@@ -137,7 +137,6 @@ std::unique_ptr<JSRuntime> HermesInstance::createJSRuntime(
                             .withAllocInYoung(false)
                             .withRevertToYGAtTTI(true)
                             .build())
-          .withES6Proxy(false)
           .withEnableSampleProfiling(true)
           .withMicrotaskQueue(ReactNativeFeatureFlags::enableMicrotasks())
           .withVMExperimentFlags(vmExperimentFlags);