Allow self-serve account closure when user has purchases

[guarani]

When a user wishes to close their WP.com account, they can do so if they have no active purchases. If they do have active purchases, they are directed to contact support.

We could instead do what WP.com does when users on the web wish to close their account: Redirect them to https://wordpress.com/me/purchases so they can cancel their purchases on their own.

Internal ref: p1692367691448459/1692309258.915019-slack-C05ALSVN5K5