fix(extension): allow copy extensions to user task

[pinussilvestrus]

Related to https://github.com/bpmn-io/bpmn-js-properties-panel/issues/738

npx @bpmn-io/sr camunda/camunda-bpmn-js -l camunda-cloud/zeebe-bpmn-moddle#738-lost-task-headers -c "npm run start:cloud"