[Mailer] Fix usage of stream_set_timeout in case of microseconds

Transport/Smtp/Stream/SocketStream.php

@@ -160,7 +160,7 @@ public function initialize(): void
         }
 
         stream_set_blocking($this->stream, true);
-        stream_set_timeout($this->stream, $timeout);
+        stream_set_timeout($this->stream, (int) $timeout, (int) (($timeout - (int) $timeout) * 1000000));
         $this->in = &$this->stream;
         $this->out = &$this->stream;
     }