don't trigger "internal" deprecations for PHPUnit Stub objects

Author: xabbuh

src/Symfony/Component/ErrorHandler/DebugClassLoader.php

@@ -18,6 +18,7 @@
 use Phake\IMock;
 use PHPUnit\Framework\MockObject\Matcher\StatelessInvocation;
 use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\MockObject\Stub;
 use Prophecy\Prophecy\ProphecySubjectInterface;
 use ProxyManager\Proxy\ProxyInterface;
 use Symfony\Component\DependencyInjection\Argument\LazyClosure;
@@ -253,6 +254,7 @@ public static function checkClasses(): bool
 
             for (; $i < \count($symbols); ++$i) {
                 if (!is_subclass_of($symbols[$i], MockObject::class)
+                    && !is_subclass_of($symbols[$i], Stub::class)
                     && !is_subclass_of($symbols[$i], ProphecySubjectInterface::class)
                     && !is_subclass_of($symbols[$i], Proxy::class)
                     && !is_subclass_of($symbols[$i], ProxyInterface::class)