Add assertion for method calling

Ref https://github.com/tc39/test262/pull/2150#discussion_r285706248

src/class-elements/private-method-shadowed-by-getter-on-nested-class.case

@@ -39,3 +39,6 @@ assert.sameValue(c.method(), 'outer class');
 assert.throws(TypeError, function() {
   innerB.method(c);
 }, 'accessed inner class getter from an object of outer class');
+assert.throws(TypeError, function() {
+  C.prototype.method.call(innerB);
+});