Merge branch '6.4' into 7.0

* 6.4:
  [Mime] Fix lowest versions of deps
  [VarDumper] Fix calling scope detection inside magic accessors
  [Validator] add missing German translations
  fix deprecation versions
  update the Brevo SMTP host
  Remove \ReflectionProperty::setAccessible(true) calls
  [Serializer] Fix denormalizing abstract part headers in MimeMessageNormalizer
  Fix property must not be accessed before initialization on SymfonyRuntime::$input
  [Form] Remove an obsolete phpdoc comment
  [Webhook] Allow slash in webhook type
  Use more "First class callable syntax" + Normalize set_error_handler/set_exception_handler calls
  [FrameworkBundle][Workflow] Throw exception is workflow.xxx.transitions is not an array

Author: nicolas-grekas

Tests/Transport/RoundRobinTransportTest.php

@@ -62,7 +62,6 @@ public function testSendAllDead()
         $t2->expects($this->once())->method('send')->will($this->throwException(new TransportException()));
         $t = new RoundRobinTransport([$t1, $t2]);
         $p = new \ReflectionProperty($t, 'cursor');
-        $p->setAccessible(true);
         $p->setValue($t, 0);
 
         try {

Tests/Transport/Smtp/SmtpTransportTest.php

@@ -162,7 +162,6 @@ private function invokeAssertResponseCode(string $response, array $codes): void
     {
         $transport = new SmtpTransport($this->getMockForAbstractClass(AbstractStream::class));
         $m = new \ReflectionMethod($transport, 'assertResponseCode');
-        $m->setAccessible(true);
         $m->invoke($transport, $response, $codes);
     }