Merge branch '6.3' into 6.4

* 6.3:
  always pass microseconds to usleep as integers
  Bump Symfony version to 6.3.11
  Update VERSION for 6.3.10
  Update CHANGELOG for 6.3.10
  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);
     }