XDocument: removed dependency on Namespace deprecated interface

gxml/XDocument.vala

@@ -93,7 +93,6 @@ public class GXml.XDocument : GXml.XNode,
   // GXml.DomNode
   public override Gee.Map<string,GXml.DomNode> attrs { owned get { return new XHashMapAttr (this, (Xml.Node*) doc) as Gee.Map<string,GXml.DomNode>; } }
   public override Gee.BidirList<GXml.DomNode> children_nodes { owned get { return new XListChildren (this, (Xml.Node*) doc) as Gee.BidirList<GXml.DomNode>; } }
-  public override Gee.List<GXml.Namespace> namespaces { owned get { return new XListNamespaces (this, doc->get_root_element()) as Gee.List<GXml.Namespace>; } }
   public override GXml.DomDocument document { get { return this; } }
   // GXml.DomDocument
   public bool indent { get; set; default = false; }