Add conflict for knplabs/knp-menu-bundle 3.4.0

[lukasbableck]

knplabs/knp-menu-bundle 3.4.0 breaks the Contao backend

There is already an issue for this: KnpLabs/KnpMenuBundle#476
contao/contao#7118

Twig\Error\LoaderError:
Template "@KnpMenu/menu.html.twig" is not defined.

  at vendor/contao/core-bundle/templates/Backend/be_menu.html.twig:13
  at Twig\Loader\ChainLoader->getCacheKey()
     (vendor/twig/twig/src/Environment.php:264)
  at Twig\Environment->getTemplateClass()
     (vendor/twig/twig/src/Environment.php:312)
  at Twig\Environment->load()
     (vendor/twig/twig/src/Environment.php:280)
  at Twig\Environment->render()
     (vendor/knplabs/knp-menu/src/Knp/Menu/Renderer/TwigRenderer.php:41)
  at Knp\Menu\Renderer\TwigRenderer->render()
     (vendor/knplabs/knp-menu/src/Knp/Menu/Twig/Helper.php:77)
  at Knp\Menu\Twig\Helper->render()
     (vendor/knplabs/knp-menu/src/Knp/Menu/Twig/MenuExtension.php:73)
  at Knp\Menu\Twig\MenuExtension->render()
     (var/cache/dev/twig/ef/efc14d73630c4389d0cd029232cb0f0a.php:76)
  at __TwigTemplate_c23512656e4601c5c052bbb46372c513->doDisplay()
     (vendor/twig/twig/src/Template.php:394)
  at Twig\Template->displayWithErrorHandling()
     (vendor/twig/twig/src/Template.php:367)
  at Twig\Template->display()
     (vendor/twig/twig/src/Template.php:379)
  at Twig\Template->render()
     (vendor/twig/twig/src/TemplateWrapper.php:38)
  at Twig\TemplateWrapper->render()
     (vendor/twig/twig/src/Environment.php:280)
  at Twig\Environment->render()
     (vendor/contao/core-bundle/contao/controllers/BackendMain.php:240)
  at Contao\BackendMain->compileTemplateData()
     (vendor/contao/core-bundle/contao/controllers/BackendMain.php:198)
  at Contao\BackendMain->output()
     (vendor/contao/core-bundle/contao/controllers/BackendMain.php:148)
  at Contao\BackendMain->run()
     (vendor/contao/core-bundle/src/Controller/BackendController.php:44)
  at Contao\CoreBundle\Controller\BackendController->mainAction()
     (vendor/symfony/http-kernel/HttpKernel.php:181)
  at Symfony\Component\HttpKernel\HttpKernel->handleRaw()
     (vendor/symfony/http-kernel/HttpKernel.php:76)
  at Symfony\Component\HttpKernel\HttpKernel->handle()
     (vendor/symfony/http-kernel/Kernel.php:197)
  at Symfony\Component\HttpKernel\Kernel->handle()
     (public/index.php:42) 

[leofeyer]

@bytehead Can you reproduce the issue?

[bytehead]

Yes 👍

[leofeyer]

Thank you @lukasbableck.