Update XmlDocument.xml (#9364)

Typo corrected

Author: praveen-x

xml/System.Xml/XmlDocument.xml

@@ -167,7 +167,7 @@
   
 <a name="Navigate"></a>   
 ## Navigate the document tree  
- You can use properties to navigate around an XML document. But before you use any of them, let's quickly review a few terms. Your document is composed of nodes. Each node has as single *parent* node directly above it. The only node that does not have a parent node is the document root, as it is the top-level node. Most nodes can have *child* nodes, which are nodes directly below them. Nodes that are at the same level are *siblings*.  
+ You can use properties to navigate around an XML document. But before you use any of them, let's quickly review a few terms. Your document is composed of nodes. Each node has a single *parent* node directly above it. The only node that does not have a parent node is the document root, as it is the top-level node. Most nodes can have *child* nodes, which are nodes directly below them. Nodes that are at the same level are *siblings*.  
   
  The following examples show you how to obtain the root node, jump to the first child node of the root node, access any of its child nodes, get back out to the parent node, and then navigate across sibling nodes.