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

[h1alexbel]

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This version is outdated!For the latest version, please look at [https://www.w3.org/TR/xml11/.](https://www.w3.org/TR/xml11/)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

[h1alexbel]

@yegor256 new bug