Merge branch '5.4' into 6.3

* 5.4:
  always pass microseconds to usleep as integers
  Bump Symfony version to 5.4.34
  Update VERSION for 5.4.33
  Update CONTRIBUTORS for 5.4.33
  Update CHANGELOG for 5.4.33

Author: derrabus

Transport/AbstractTransport.php

@@ -129,7 +129,7 @@ private function checkThrottling(): void
         $sleep = (1 / $this->rate) - (microtime(true) - $this->lastSent);
         if (0 < $sleep) {
             $this->logger->debug(sprintf('Email transport "%s" sleeps for %.2f seconds', __CLASS__, $sleep));
-            usleep($sleep * 1000000);
+            usleep((int) ($sleep * 1000000));
         }
         $this->lastSent = microtime(true);
     }