MaharaAuthPlugin: removing default text for dbtype

MaharaAuthPlugin.php

@@ -47,7 +47,7 @@ class MaharaAuthPlugin extends AuthPlugin {
 	var $dbuser;
 	var $dbpass;
 
-    public function __construct($dbname, $host='localhost',$dbtype='postgres', $user='', $password='', $prefix='') {
+    public function __construct($dbname, $host='localhost',$dbtype='', $user='', $password='', $prefix='') {
         $this->dbname = $dbname;
         $this->host = $host;
         $this->prefix = $prefix;