Merge branch '6.3' into 6.4

* 6.3:
  [VarDumper] Fix CSS alignment in HtmlDumper
  allow environment variables starting with an underscore
  Update a test
  [Mailer][Postmark] Add missing changelog for webhook support
  Remove #StandWithUkraine
  [Notifier][Smsc] Require login and password

Author: fabpot

SmscTransport.php

@@ -34,9 +34,9 @@ final class SmscTransport extends AbstractTransport
     private ?string $password;
     private string $from;
 
-    public function __construct(?string $username, #[\SensitiveParameter] ?string $password, string $from, HttpClientInterface $client = null, EventDispatcherInterface $dispatcher = null)
+    public function __construct(string $login, #[\SensitiveParameter] string $password, string $from, HttpClientInterface $client = null, EventDispatcherInterface $dispatcher = null)
     {
-        $this->login = $username;
+        $this->login = $login;
         $this->password = $password;
         $this->from = $from;