Default value of `appliesOnSubscription` changed to `true` for app discount inputs

The default value of appliesOnSubscription has been changed from false to true on the DiscountCodeAppInput and DiscountAutomaticAppInput input types in GraphQL Admin API.

No action is required. This default value change has no effect on how discounts are applied at checkout. If your app explicitly sets appliesOnSubscription when creating or updating app discounts, your behavior is unchanged.

This change applies across all active API versions. The appliesOnOneTimePurchase field already defaults to true and is unchanged.