Remove unnecessary css reference in ads-system library

After clear cache, LibraryDiscoveryParser reproduce warring

Warning: Invalid argument supplied for foreach() in Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension() (line 148 of core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php).
Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension('ads_system') (Line: 87)
Drupal\Core\Asset\LibraryDiscoveryCollector->getLibraryDefinitions('ads_system') (Line: 66)
Drupal\Core\Asset\LibraryDiscoveryCollector->resolveCacheMiss('ads_system') (Line: 149)
Drupal\Core\Cache\CacheCollector->get('ads_system') (Line: 44)
Drupal\Core\Asset\LibraryDiscovery->getLibrariesByExtension('ads_system') (Line: 58)
Drupal\Core\Asset\LibraryDiscovery->getLibraryByName('ads_system', 'ads-system') (Line: 54)
Drupal\Core\Asset\LibraryDependencyResolver->doGetDependencies(Array) (Line: 31)
Drupal\Core\Asset\LibraryDependencyResolver->getLibrariesWithDependencies(Array) (Line: 104)
Drupal\Core\Asset\AssetResolver->getLibrariesToLoad(Object) (Line: 116)
Drupal\Core\Asset\AssetResolver->getCssAssets(Object, ) (Line: 291)
Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAssetLibraries(Object, Array) (Line: 161)
Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAttachments(Object) (Line: 45)
Drupal\Core\EventSubscriber\HtmlResponseSubscriber->onRespond(Object, 'kernel.response', Object)
call_user_func(Array, Object, 'kernel.response', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.response', Object) (Line: 191)
Symfony\Component\HttpKernel\HttpKernel->filterResponse(Object, Object, 1) (Line: 173)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 46)
Drupal\relaxed\StackMiddleware\RequestFormatSetter->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 693)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)