`plan` is missing on `Stripe.Subscription` type

Describe the bug

The Stripe.Subscription type does not match the data returned from stripe.subscriptions.retrieve().

To Reproduce

import Stripe from 'stripe';

const stripe = new Stripe(import.meta.env.STRIPE_SECRET_KEY!);

// ... in a function
const subscription = await stripe.subscriptions.retrieve(subscriptionId);
const productId = subscription.plan.product;
/*                             ^^^^
                               TS error that plan doesn't exist on 
                               Stripe.Subscription, but it exists */

Expected behavior

The plan data is present, so the type should reflect that.

Code snippets

No response

OS

macOS

Node version

Node v22.1.0

Library version

stripe-node@^16.2.0

API version

n/a

Additional context