When changin a product within a subscription that has a coupon applied, the coupon isn't applied to the new product unless you re-add it

[guicmazeredo]

Description

After changing the subscription product within a subscription that has a recurring coupon applied, the coupon isn't applied to the new product after clicking "Recalculate". You need to re-add the coupon for it to work.
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Testing instructions

1. Sign up for a subscription product with a coupon code.
2. On the site dashboard, go to Subscriptions and edit the subscription in question.
3. Remove the product from the subscription and add another product.
4. Click "Recalculate"
5. Notice that the recurring totals are updated but without the coupon discount.
6. Remove the coupon and re-add it.
7. Notice the discount will be applied.

Video: https://www.loom.com/share/4255c3d6709e407094160694b0a362fe?sid=8a670c68-ceec-4f45-8a55-6de51dba07d9

Product impact

This issue requires more time from merchants when editing subscriptions with coupons.

• [Yes] Does this feature affect WooCommerce Subscriptions?
• [No] Does this feature affect WooCommerce Payments?

Additional context

This was reported by a customer in 9172088-zd