patterns: `kindOf` incorrectly looks at properties inherited from Object.prototype

[gibson042]

Describe the bug

kindOf does not adequately guard against Object.prototype property reads.

Steps to reproduce

import '@endo/init';
import { kindOf } from '@endo/patterns';
import { makeTagged } from '@endo/pass-style';

const goodTagged = makeTagged('foo', undefined);
console.log(kindOf(goodTagged));
// => undefined

const badTagged = makeTagged('valueOf', undefined);
console.log(kindOf(badTagged));
// => TypeError: matchHelper.checkIsWellFormed is not a function

Expected behavior

Object.prototype properties are not confused as helpers.