Add %AsyncFunction.prototype% test

test/built-ins/AsyncFunction/AsyncFunctionPrototype-is-not-callable.js

@@ -0,0 +1,28 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-async-function-prototype-properties
+description: >
+  %AsyncFunction.prototype% is an ordinary non-callable object.
+info: |
+  Properties of the AsyncFunction Prototype Object
+
+  The AsyncFunction prototype object:
+
+  [...]
+  * is an ordinary object.
+  * is not a function object and does not have an [[ECMAScriptCode]] internal slot
+    or any other of the internal slots listed in Table 28.
+features: [async-functions]
+---*/
+
+var AsyncFunctionPrototype = Object.getPrototypeOf(async function() {});
+
+assert.sameValue(typeof AsyncFunctionPrototype, "object");
+assert.throws(TypeError, function() {
+  AsyncFunctionPrototype();
+});
+
+assert(!AsyncFunctionPrototype.hasOwnProperty("length"), "length");
+assert(!AsyncFunctionPrototype.hasOwnProperty("name"), "name");