Removes the specified xtype from the {@link #whitelist}.
@param {String/String[]} xtype Removes the xtype(s) from the {@link #whitelist}.
function(xtype) {
        var me = this;

        if (Ext.isArray(xtype)) {
            Ext.Array.forEach(xtype, me.removeXTypeFromWhitelist, me);
            return;
        }

        Ext.Array.remove(me.whitelist, xtype);
    }