Merge branch '6.4' into 7.2

* 6.4:
  Remove unneeded use statements
  Redundant assignment to promoted property
  Revert "[Messenger] Add call to `gc_collect_cycles()` after each message is handled"

Author: fabpot

Tests/SerializerTest.php

@@ -65,7 +65,6 @@
 use Symfony\Component\Serializer\Tests\Fixtures\DummyObjectWithEnumProperty;
 use Symfony\Component\Serializer\Tests\Fixtures\DummyWithObjectOrNull;
 use Symfony\Component\Serializer\Tests\Fixtures\DummyWithVariadicParameter;
-use Symfony\Component\Serializer\Tests\Fixtures\DummyWithVariadicProperty;
 use Symfony\Component\Serializer\Tests\Fixtures\FalseBuiltInDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\FooImplementationDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\FooInterfaceDummyDenormalizer;