PHP 8.2 Deprecations

Problem/Motivation

PHP 8.2 Deprecations result in warnings

Steps to reproduce

Install module on a Drupal 10 site running on PHP 8.2. The following error appears

Deprecated function: Creation of dynamic property Drupal\react_webform_backend\Plugin\rest\resource\WebformSubmitResource::$entityTypeManager is deprecated in Drupal\react_webform_backend\Plugin\rest\resource\WebformSubmitResource::create() (line 45 of modules/contrib/react_webform_backend/src/Plugin/rest/resource/WebformSubmitResource.php). 

Proposed resolution

Fix deprecations