Issue #3126569 by mondrake, longwave: Replace usage of assertAttributeEmpty() that is deprecated

(cherry picked from commit 0bfda930)

core/modules/locale/tests/src/Unit/LocaleTranslationTest.php

@@ -50,8 +50,7 @@ protected function setUp() {
   public function testDestruct() {
     $translation = new LocaleTranslation($this->storage, $this->cache, $this->lock, $this->getConfigFactoryStub(), $this->languageManager, $this->requestStack);
     // Prove that destruction works without errors when translations are empty.
-    $this->assertAttributeEmpty('translations', $translation);
-    $translation->destruct();
+    $this->assertNull($translation->destruct());
   }
 
 }

core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php

@@ -28,7 +28,6 @@ trait PHPUnit8Warnings {
     'getObjectAttribute() is deprecated and will be removed in PHPUnit 9.',
     'assertAttributeEquals() is deprecated and will be removed in PHPUnit 9.',
     'assertAttributeInstanceOf() is deprecated and will be removed in PHPUnit 9.',
-    'assertAttributeEmpty() is deprecated and will be removed in PHPUnit 9.',
     'The optional $ignoreCase parameter of assertContains() is deprecated and will be removed in PHPUnit 9.',
     'The optional $ignoreCase parameter of assertNotContains() is deprecated and will be removed in PHPUnit 9.',
   ];