Remove unused comment

Author: Valentin Prugnaud

src/LaunchDarkly/LDClient.php

@@ -281,7 +281,6 @@ public function secureModeHash($user) {
 
     /**
      * Publish events to LaunchDarkly
-     * @param $payload string Event payload
      * @return bool Whether the events were successfully published
      */
     public function flush()