CiviCRM 5.39 support

The tests do not pass on 5.39.

There were 3 errors:

1) GoCardlessTest::testWebhookPaymentConfirmationFirst
CiviCRM_API3_Exception: Not having valid line items for membership payments is invalid.

/buildkit/build/dmaster/web/sites/all/modules/civicrm/api/api.php:134
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:281
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:196
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/tests/phpunit/GoCardlessTest.php:935
/buildkit/extern/phpunit7/phpunit7.phar:615

2) GoCardlessTest::testWebhookPaymentConfirmationSubsequent
CiviCRM_API3_Exception: Not having valid line items for membership payments is invalid.

/buildkit/build/dmaster/web/sites/all/modules/civicrm/api/api.php:134
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:465
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:297
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:196
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/tests/phpunit/GoCardlessTest.php:1069
/buildkit/extern/phpunit7/phpunit7.phar:615

3) GoCardlessTest::testWebhookPaymentConfirmationDoesNotMarkCancelledAsInProgress
CiviCRM_API3_Exception: Not having valid line items for membership payments is invalid.

/buildkit/build/dmaster/web/sites/all/modules/civicrm/api/api.php:134
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:465
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:297
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/CRM/Core/Payment/GoCardlessIPN.php:196
/buildkit/build/dmaster/web/sites/default/files/civicrm/ext/gocardless/tests/phpunit/GoCardlessTest.php:1201
/buildkit/extern/phpunit7/phpunit7.phar:615

ERRORS!
Tests: 37, Assertions: 198, Errors: 3.