Update item[string] property

Author: Jan Jahoda

xml/System.Net/WebHeaderCollection.xml

@@ -1482,13 +1482,16 @@
         <ReturnType>System.String</ReturnType>
       </ReturnValue>
       <Parameters>
-        <Parameter Name="name" Type="System.String" Index="0" FrameworkAlternate="dotnet-uwp-10.0;net-5.0;netcore-1.0;netcore-1.1;netcore-2.0;netcore-2.1;netcore-2.2;netcore-3.0;netcore-3.1;netstandard-2.1" />
+        <Parameter Name="name" Type="System.String" Index="0" FrameworkAlternate="dotnet-uwp-10.0;netcore-1.0;netcore-1.1;netstandard-2.1" />
       </Parameters>
       <Docs>
-        <param name="name">To be added.</param>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
+        <param name="name">Header name.</param>
+        <summary>Gets or sets the specified response header.</summary>
+        <value>A <see cref="T:System.String" /> instance containing the specified header.</value>
         <remarks>To be added.</remarks>
+        <exception cref="T:System.ArgumentOutOfRangeException">The length of <paramref name="value" /> is greater than 65535.</exception>
+        <exception cref="T:System.InvalidOperationException">This <see cref="T:System.Net.WebHeaderCollection" /> instance does not allow instances of <see cref="T:System.Net.HttpResponseHeader" />.</exception>
+        <exception cref="T:System.NullReferenceException">The <paramref name="name" /> is null.</exception>
       </Docs>
     </Member>
     <Member MemberName="Keys">