Site Editor Compatibility: Stripe connect flow does not redirect to site-editor

In the new site editor in Gutenberg (`/wp-admin/admin.php?page=gutenberg-edit-site`), the Connect to Stripe flow does not redirect back to the site-editor as a user might expect.

#### Steps to reproduce the issue

1. With the Gutenberg plugin active (>=10.4.0-rc1), activate a block-ready theme (like tt1-blocks)
2. Upgrade your site to a Premium plan to avoid upgrade nudges.
3. Insert a Payments block (or any other block requiring a Stripe connection) in the footer. You should see the Connect Stripe button in the toolbar.
4. Click the Connect Stripe button to enter the Stripe connection flow.
5. Either connect a Stripe account or select "Skip this form" if you have the store sandboxed, in order to complete the Stripe connection.

#### What I expected
After successful Stripe connection, I would expect to be redirected back to the site-editor, and my changes should have been saved (ie the Payments block should still be in the footer, now without an upgrade nudge)

#### What happened instead
After upgrading I was redirected to the Earn page (`https://wordpress.com/earn/payments/stacifakefsesite.wordpress.com?stripe_connect_success=gutenberg`). When I re-entered the site editor, my changes had not been saved (the Payments block was no longer in the footer).

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