Chakracore: Update `Object.getOwnPropertyDescriptors` with spec changes

[ljharb]

Per https://github.com/tc39/ecma262/pull/593 - if the result of [[GetOwnPropertyDescriptor]] is undefined, it should _not_ be stored on the returned descriptors object.

[ianwjhalliday]

it should not _not_ be stored

@ljharb double not intentional or typo? That is to clarify, you are saying it should be stored on the returned descriptors object?

fyi @jordonwii

[ljharb]

Typo, sorry - updated.

undefined descriptors must not be present on the return of Object.getOwnPropertyDescriptors.

[ianwjhalliday]

@ljharb cool

@jordonwii want to take this?

[j-wing]

@ianwjhalliday Yep - it should be a straightforward change.