[NFC] Fix UpdateSubscriptionTest on php8 by creating a Payment Processor

[seamuslee001]

Overview

This fixes the following the following test error on php8

CRM_Contribute_Form_UpdateSubscriptionTest::testMail
Failure in api call for Order create:  Error in call to Payment_create : Undefined array key "updateSubscriptionBillingUrl"
#0 /home/jenkins/bknix-edge/build/build-2/web/sites/all/modules/civicrm/CRM/Financial/BAO/Payment.php(189): civicrm_api3('Contribu

Before

Test fails on php8

After

Test passes on php8

ping @eileenmcnaughton

[civibot]

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[eileenmcnaughton]

@seamuslee001 I'm OK to merge this to get the test 'out of your hair' - but it should work without a processor