Subscriptions: fix site address field to show primary site address in the subscription payment receipt email

### Impacted plugin

Jetpack

### What

Fix the site address field to show primary site address in the subscription payment receipt email

### How

When a user subscribes to the site using Monthly Subscription Payment Block, in the payment receipt email they receive they currently see old internal site address - .wordpress.com site address.

For example the subscribers of the site https://inmateblogger.com/ see the following (old free site address) in their subscription payment receipt email:

We have 3 requests from users requesting the site address in such payment receipt emails to be the default site address.

No file, test, or entry point is named in the issue. Trace the Monthly Subscription Payment Block flow that generates the subscription payment receipt email, then verify that the receipt displays the site's primary address rather than its old internal .wordpress.com address.

Written by the indexing model from the issue text.