6 files declare their use of WorkflowTransition in State Machine 8

FulfillmentGuard.php in tests/modules/state_machine_test/src/Guard/FulfillmentGuard.php

GenericGuard.php in tests/modules/state_machine_test/src/Guard/GenericGuard.php

GuardInterface.php in src/Guard/GuardInterface.php

StateItem.php in src/Plugin/Field/FieldType/StateItem.php

StateItemInterface.php in src/Plugin/Field/FieldType/StateItemInterface.php

WorkflowTransitionEvent.php in src/Event/WorkflowTransitionEvent.php