fix: remove dead promise polyfill import

Since Hermes is the only supported JS engine and always provides a native
Promise implementation, the `else` branch in polyfillPromise.js that
imports the `promise` package via `../Promise` is dead code that can
never execute (`hasPromise()` is always true).

This dead import causes the bundler to include the entire `promise`
package (~15KB) in every app's JS bundle despite it never being used.

Remove the dead branch and the unused `polyfillGlobal` import.

Fixes #57702

Author: stareezy-1

packages/react-native/Libraries/Core/polyfillPromise.js

@@ -10,29 +10,22 @@
 
 'use strict';
 
-const {polyfillGlobal} = require('../Utilities/PolyfillFunctions');
-
 /**
- * Set up Promise. The native Promise implementation throws the following error:
- * ERROR: Event loop not supported.
+ * Set up Promise. Hermes provides a native Promise implementation that
+ * satisfies all requirements of React Native.
  *
  * If you don't need these polyfills, don't use InitializeCore; just directly
  * require the modules you need from InitializeCore for setup.
  */
 
-// If global.Promise is provided by Hermes, we are confident that it can provide
-// all the methods needed by React Native, so we can directly use it.
-if (global?.HermesInternal?.hasPromise?.()) {
-  const HermesPromise = global.Promise;
+// Hermes is the only supported JS engine and always provides Promise natively.
+const HermesPromise = global.Promise;
 
-  if (__DEV__) {
-    if (typeof HermesPromise !== 'function') {
-      console.error('HermesPromise does not exist');
-    }
-    global.HermesInternal?.enablePromiseRejectionTracker?.(
-      require('../promiseRejectionTrackingOptions').default,
-    );
+if (__DEV__) {
+  if (typeof HermesPromise !== 'function') {
+    console.error('HermesPromise does not exist');
   }
-} else {
-  polyfillGlobal('Promise', () => require('../Promise').default);
+  global.HermesInternal?.enablePromiseRejectionTracker?.(
+    require('../promiseRejectionTrackingOptions').default,
+  );
 }