Broken definition of 'set_margin' at QRCodeConfigurationForm

Problem/Motivation

On Drupal core version 11.3.6 I was updating drupal/endroid_qr_code to version 4.0.1 and faced following error when tried to read module's configuration form:

InvalidArgumentException: "required" is an invalid render array key. Value should be an array but got a boolean. in Drupal\Core\Render\Element::children() (line 97 of core/lib/Drupal/Core/Render/Element.php).
Drupal\Core\Form\ConfigFormBase->loadDefaultValuesFromConfig() (Line: 117)
Drupal\Core\Form\ConfigFormBase->loadDefaultValuesFromConfig() (Line: 1065)
Drupal\Core\Form\FormBuilder->doBuildForm() (Line: 597)
Drupal\Core\Form\FormBuilder->processForm() (Line: 347)
Drupal\Core\Form\FormBuilder->buildForm() (Line: 73)
Drupal\Core\Controller\FormController->getContentResult()
call_user_func_array() (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber::wrapControllerExecutionInRenderContext():121}() (Line: 634)
Drupal\Core\Render\Renderer::{closure:Drupal\Core\Render\Renderer::executeInRenderContext():634}()
Fiber->start() (Line: 635)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 121)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber::onController():96}() (Line: 183)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 54)
Drupal\simple_oauth\HttpMiddleware\BasicAuthSwap->handle() (Line: 53)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 118)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 92)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 53)
Asm89\Stack\Cors->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 53)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 54)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 745)
Drupal\Core\DrupalKernel->handle() (Line: 19)

After closer look on QRCodeConfigurationForm I confirmed that 'set_margin' form element render array has incorrectly defined 'required' parameter.

Steps to reproduce

With drupal/endroid_qr_code module version 4.0.1 installed, try to reach /admin/config/endroid_qr_code as admin

Proposed resolution

Fix definition of 'set_margin' QRCodeConfigurationForm form element: 'required' -> '#required'