nextcloud-mephi/settings/ajax/removegroup.php

<?php

OC_JSON::checkAdminUser();
OCP\JSON::callCheck();

$name = $_POST["groupname"];

// Return Success story
if( OC_Group::deleteGroup( $name )) {
	OC_JSON::success(array("data" => array( "groupname" => $name )));
}
else{
	OC_JSON::error(array("data" => array( "message" => $l->t("Unable to delete group") )));
}