Error after trying to add new legal document

Problem/Motivation

New legal document cannot be created. Error:

```
The website encountered an unexpected error. Please try again later.
TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function "Drupal\path\Plugin\Field\FieldWidget\PathWidget" not found or invalid function name in call_user_func_array() (line 282 of core/lib/Drupal/Core/Form/FormValidator.php).

call_user_func_array('Drupal\path\Plugin\Field\FieldWidget\PathWidget', Array) (Line: 282)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object) (Line: 238)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object, 'entity_legal_document_add_form') (Line: 118)
Drupal\Core\Form\FormValidator->validateForm('entity_legal_document_add_form', Array, Object) (Line: 588)
Drupal\Core\Form\FormBuilder->processForm('entity_legal_document_add_form', Array, Object) (Line: 320)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 564)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 158)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 80)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 264)
Drupal\shield\ShieldMiddleware->bypass(Object, 1, 1) (Line: 221)
Drupal\shield\ShieldMiddleware->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 708)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)
```

Steps to reproduce

1. Fresh install with composer and activate the module (drupal 9.3.4)
2. Try to create a new legal document (/admin/structure/legal/add)
3. Save
4. => error occurs
5. No legal document has been created

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes