Update XmlReader.xml (dotnet#9115)

Changed "child element" to "descendant element".

Author: zacharylayne

xml/System.Xml/XmlReader.xml

@@ -8587,7 +8587,7 @@ An <see cref="T:System.Xml.XmlReader" /> method was called before a previous asy
         <param name="name">The qualified name of the element you wish to move to.</param>
         <summary>Advances the <see cref="T:System.Xml.XmlReader" /> to the next descendant element with the specified qualified name.</summary>
         <returns>
-          <see langword="true" /> if a matching descendant element is found; otherwise <see langword="false" />. If a matching child element is not found, the <see cref="T:System.Xml.XmlReader" /> is positioned on the end tag (<see cref="P:System.Xml.XmlReader.NodeType" /> is <see langword="XmlNodeType.EndElement" />) of the element.
+          <see langword="true" /> if a matching descendant element is found; otherwise <see langword="false" />. If a matching descendant element is not found, the <see cref="T:System.Xml.XmlReader" /> is positioned on the end tag (<see cref="P:System.Xml.XmlReader.NodeType" /> is <see langword="XmlNodeType.EndElement" />) of the element.
 
  If the <see cref="T:System.Xml.XmlReader" /> is not positioned on an element when <see cref="M:System.Xml.XmlReader.ReadToDescendant(System.String)" /> was called, this method returns <see langword="false" /> and the position of the <see cref="T:System.Xml.XmlReader" /> is not changed.</returns>
         <remarks>
@@ -8653,7 +8653,7 @@ An <see cref="T:System.Xml.XmlReader" /> method was called before a previous asy
         <param name="namespaceURI">The namespace URI of the element you wish to move to.</param>
         <summary>Advances the <see cref="T:System.Xml.XmlReader" /> to the next descendant element with the specified local name and namespace URI.</summary>
         <returns>
-          <see langword="true" /> if a matching descendant element is found; otherwise <see langword="false" />. If a matching child element is not found, the <see cref="T:System.Xml.XmlReader" /> is positioned on the end tag (<see cref="P:System.Xml.XmlReader.NodeType" /> is <see langword="XmlNodeType.EndElement" />) of the element.
+          <see langword="true" /> if a matching descendant element is found; otherwise <see langword="false" />. If a matching descendant element is not found, the <see cref="T:System.Xml.XmlReader" /> is positioned on the end tag (<see cref="P:System.Xml.XmlReader.NodeType" /> is <see langword="XmlNodeType.EndElement" />) of the element.
 
  If the <see cref="T:System.Xml.XmlReader" /> is not positioned on an element when <see cref="M:System.Xml.XmlReader.ReadToDescendant(System.String,System.String)" /> was called, this method returns <see langword="false" /> and the position of the <see cref="T:System.Xml.XmlReader" /> is not changed.</returns>
         <remarks>To be added.</remarks>