files, folders, documents: remove client_id post from edit and link modals as it should get the client_id in post, enforceClientAccess

agent/post/document_model.php

@@ -1,7 +1,6 @@
 <?php
 defined('FROM_POST_HANDLER') || die("Direct file access is not allowed");
 
-$client_id = intval($_POST['client_id']);
 $name = sanitizeInput($_POST['name']);
 $folder = intval($_POST['folder']);
 $description = sanitizeInput($_POST['description']);