Fix wrong prototype of unscopables

Unscopable is supposed to have a null prototype.

Author: Sebmaster

lib/constructs/interface.js

@@ -1257,6 +1257,8 @@ class Interface {
       }
     }
     if (Object.keys(unscopables).length > 0) {
+      // eslint-disable-next-line no-proto
+      unscopables.__proto__ = null;
       this.addProperty("prototype", Symbol.unscopables, JSON.stringify(unscopables), {
         writable: false
       });

test/__snapshots__/test.js.snap

@@ -6670,7 +6670,7 @@ Object.defineProperties(Unscopable.prototype, {
   unscopableTest: { enumerable: true },
   unscopableMixin: { enumerable: true },
   [Symbol.toStringTag]: { value: \\"Unscopable\\", configurable: true },
-  [Symbol.unscopables]: { value: { unscopableTest: true, unscopableMixin: true }, configurable: true }
+  [Symbol.unscopables]: { value: { unscopableTest: true, unscopableMixin: true, __proto__: null }, configurable: true }
 });
 const iface = {
   // When an interface-module that implements this interface as a mixin is loaded, it will append its own \`.is()\`