fetchAll() Error With DBAL 4 (Work with DBAL 3)

$allusersemail='';
$conn = $GLOBALS["Conn"];
$sql = "SELECT DISTINCT EmplloyEmail FROM Notifications
WHERE Jlsat = 1 ";
$rows = $conn->executeQuery($sql)->fetchAll();
foreach ($rows as $row) {
$allusersemail .= $row['EmplloyEmail'].',';
}

what i do with the code how i change it ?

You better read DBAL 4 Upgrade Guide on Removed FetchMode and the corresponding methods.