Hide Sofort from the settings page when it's disabled and UPE is enabled

[a-danae]

Changes proposed in this Pull Request:

• When Sofort is disabled, hide it from the list of UPE payment methods.

Sofort showing up in the Payment methods list is a regression. Things work as expected in develop.
For some background, Sofort is being deprecated as a standalone payment method Ref. We're already hiding this payment gateway in the non-UPE experience.

Before	After

Testing instructions

1. Check out the add/deferred-intent branch.
2. Enable UPE, under the Stripe's settings tab (wp-admin/admin.php?page=wc-settings&tab=checkout&section=stripe&panel=settings) > Advanced settings > Enable the updated checkout experience
3. Enable Sofort, under the Stripe's payment methods tab (wp-admin/admin.php?page=wc-settings&tab=checkout&section=stripe&panel=methods)
4. Check out this branch and reload the Payment methods tab
5. Confirm that Sofort continues to appear on the list
6. Disable Sofort, save, and reload the page
7. Confirm that Sofort is no longer on the list

---

• Covered with tests (or have a good reason not to test in description ☝️)
• Added changelog entry in both changelog.txt and readme.txt (or does not apply)
• Tested on mobile (or does not apply)

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)

[Mayisha]

Working as expected. If Sofort is disabled, it does not show up in the payment method list for both UPE enabled/disabled states. 👍