Issue #3034015 by mondrake, Wim Leers, Mile23: Class to test deprecation error...

Issue #3034015 by mondrake, Wim Leers, Mile23: Class to test deprecation error for deprecated trait triggers deprecation error itself

(cherry picked from commit 7555529a)

core/modules/serialization/tests/src/Unit/Normalizer/TimeStampItemNormalizerTraitDeprecatedTestClass.php → core/modules/serialization/tests/serialization_test/src/TimeStampItemNormalizerTraitDeprecatedTestClass.php

 <?php
 
-namespace Drupal\Tests\serialization\Unit\Normalizer;
+namespace Drupal\serialization_test;
 
 use Drupal\serialization\Normalizer\TimeStampItemNormalizerTrait;
 

core/modules/serialization/tests/src/Unit/Normalizer/TimeStampItemNormalizerTraitDeprecatedTest.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\serialization\Unit\Normalizer;
 
+use Drupal\serialization_test\TimeStampItemNormalizerTraitDeprecatedTestClass;
 use Drupal\Tests\UnitTestCase;
 
 /**