[BUGFIX beta] Reduce false positives for HAS_NATIVE_SYMBOL with polyf…

…ills.

Prior to this change the core.js polyfills would be detected as "native
symbols" (they monkey patch `Object.prototype.toString` to avoid detection by
our prior check).

Co-authored-by: Godfrey Chan <godfreykfc@gmail.com>

packages/@ember/-internals/utils/lib/symbol-utils.ts

@@ -3,7 +3,5 @@ export const HAS_NATIVE_SYMBOL = (function() {
     return false;
   }
 
-  // use `Object`'s `.toString` directly to prevent us from detecting
-  // polyfills as native
-  return Object.prototype.toString.call(Symbol()) === '[object Symbol]';
+  return typeof Symbol() === 'symbol';
 })();