[fs] polling_interval config should be milliseconds not microseconds

regression from this commit php-enqueue/fs@c5199ca

config should be milliseconds like in docs stated.....$this->pollingInterval is holding milliseconds which is correct.

But usleep is using microseconds. To fix it just convert milliseconds to microseconds

Author: ssiergl

pkg/fs/FsConsumer.php

@@ -90,7 +90,7 @@ public function receive(int $timeout = 0): ?Message
                 return null;
             }
 
-            usleep($this->pollingInterval);
+            usleep($this->pollingInterval * 1000);
 
             if ($timeout && (microtime(true) - $startAt) >= $timeout) {
                 return null;