Cleans up all salesforce_pull tests

modules/salesforce_mapping/src/Entity/SalesforceMapping.php

...esforce_mapping/src/Entity/SalesforceMappingInterface.php

modules/salesforce_pull/src/Plugin/QueueWorker/PullBase.php

modules/salesforce_pull/src/QueueHandler.php

modules/salesforce_pull/tests/src/Unit/PullBaseTest.php

modules/salesforce_pull/tests/src/Unit/PullQueueItemTest.php

modules/salesforce_pull/tests/src/Unit/QueueHandlerTest.php