`Arg.java` uses old link to reference compatibility character ranges

in Arg.java currently we do this:

private static void range(final char chr, final int left, final int right)
    throws XmlContentException {
    if (chr >= left && chr <= right) {
        throw new XmlContentException(
            String.format(
                "Character #%02X is in the restricted XML range #%02X-#%02X, see http://www.w3.org/TR/2004/REC-xml11-20040204/#charsets",
                (int) chr, left, right
            )
        );
    }
}

However, on the website I getting this:

This version is outdated!For the latest version, please look at [https://www.w3.org/TR/xml11/.](https://www.w3.org/TR/xml11/)

Please fix

Open Arg.java and locate the range method's XmlContentException message. Replace the outdated XML 1.1 specification link with the current URL shown in the issue, then verify that the error message points to the current specification.