Merge branch '5.4' into 6.0

* 5.4:
  Fix tests
  CS fix
  CS fix
  CS fix
  CS fixes
  Bump Symfony version to 5.3.4
  Update VERSION for 5.3.3
  Update CHANGELOG for 5.3.3
  Bump Symfony version to 5.2.12
  Update VERSION for 5.2.11
  Update CHANGELOG for 5.2.11
  Bump Symfony version to 4.4.27
  Update VERSION for 4.4.26
  Update CONTRIBUTORS for 4.4.26
  Update CHANGELOG for 4.4.26

Author: nicolas-grekas

Tests/MessageBirdTransportTest.php

@@ -24,7 +24,7 @@ final class MessageBirdTransportTest extends TransportTestCase
     /**
      * @return MessageBirdTransport
      */
-    public function createTransport(?HttpClientInterface $client = null): TransportInterface
+    public function createTransport(HttpClientInterface $client = null): TransportInterface
     {
         return new MessageBirdTransport('token', 'from', $client ?? $this->createMock(HttpClientInterface::class));
     }