Fix S1075 FP: Do not raise an issue for XML namespace URIs

[mary-georgiou-sonarsource]

Description

The syntax for such an XML namespace is a URI. but it is not used to access any network resource. As such it is not subject to the problems described in S1075.

Repro steps

using System.Xml;

private static XmlNamespaceManager CreateNamespaceManager()
{
    var namespaceManager = new XmlNamespaceManager(new NameTable());   // FP
    namespaceManager.AddNamespace("ffc", "http://www.redacted.com/namespaces/ffc"); // FP
    namespaceManager.AddNamespace("dex", "http://www.redacted.com/namespaces/dex"); // FP
    return namespaceManager;
}

Follow this past issue on which namespaces should be covered: #6223

Issue initially reported here.