Update summary for NameValueHeaderValue class (#11962)

Author: gewarren

xml/System.Net.Http.Headers/NameValueHeaderValue.xml

@@ -73,7 +73,7 @@
         <AssemblyVersion>4.2.0.0</AssemblyVersion>
       </AssemblyInfo>
       <Docs>
-        <summary>Initializes a new instance of the CLASS class.</summary>
+        <summary>Initializes a new instance of the <see cref="T:System.Net.Http.Headers.NameValueHeaderValue" /> class.</summary>
       </Docs>
     </MemberGroup>
     <Member MemberName=".ctor">