WebHeaderCollection: update item[string] property (#4268)

* Update item[string] property

* Add IEnumerable.GetEnumerator description

* Update xml/System.Net/WebHeaderCollection.xml

Co-authored-by: Karel Zikmund <karelz@microsoft.com>

* Remove Index[string]

Co-authored-by: Karel Zikmund <karelz@microsoft.com>
Co-authored-by: Jan Jahoda <jajahoda@.microsoft.com>

Author: 3 people

xml/System.Net/WebHeaderCollection.xml

@@ -1448,49 +1448,7 @@
         <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>
       </Docs>
-    </Member>
-    <Member MemberName="Item">
-      <MemberSignature Language="C#" Value="public string this[string name] { get; set; }" />
-      <MemberSignature Language="ILAsm" Value=".property instance string Item(string)" />
-      <MemberSignature Language="DocId" Value="P:System.Net.WebHeaderCollection.Item(System.String)" />
-      <MemberSignature Language="VB.NET" Value="Default Public Property Item(name As String) As String" />
-      <MemberSignature Language="C++ CLI" Value="public:&#xA; property System::String ^ default[System::String ^] { System::String ^ get(System::String ^ name); void set(System::String ^ name, System::String ^ value); };" />
-      <MemberSignature Language="F#" Value="member this.Item(string) : string with get, set" Usage="System.Net.WebHeaderCollection.Item" />
-      <MemberType>Property</MemberType>
-      <AssemblyInfo>
-        <AssemblyName>System.Net.WebHeaderCollection</AssemblyName>
-        <AssemblyVersion>4.0.0.0</AssemblyVersion>
-        <AssemblyVersion>4.1.0.0</AssemblyVersion>
-        <AssemblyVersion>4.1.1.0</AssemblyVersion>
-        <AssemblyVersion>4.1.2.0</AssemblyVersion>
-        <AssemblyVersion>5.0.0.0</AssemblyVersion>
-      </AssemblyInfo>
-      <AssemblyInfo>
-        <AssemblyName>System.Net.Requests</AssemblyName>
-      </AssemblyInfo>
-      <AssemblyInfo>
-        <AssemblyName>netstandard</AssemblyName>
-        <AssemblyVersion>2.1.0.0</AssemblyVersion>
-      </AssemblyInfo>
-      <AssemblyInfo>
-        <AssemblyName>System</AssemblyName>
-      </AssemblyInfo>
-      <AssemblyInfo>
-        <AssemblyName>System.Net</AssemblyName>
-      </AssemblyInfo>
-      <ReturnValue>
-        <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" />
-      </Parameters>
-      <Docs>
-        <param name="name">To be added.</param>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
-        <remarks>To be added.</remarks>
-      </Docs>
-    </Member>
+    </Member>    
     <Member MemberName="Keys">
       <MemberSignature Language="C#" Value="public override System.Collections.Specialized.NameObjectCollectionBase.KeysCollection Keys { get; }" />
       <MemberSignature Language="ILAsm" Value=".property instance class System.Collections.Specialized.NameObjectCollectionBase/KeysCollection Keys" />
@@ -1997,8 +1955,8 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Returns an enumerator that can iterate through the <see cref="T:System.Net.WebHeaderCollection" /> instance.</summary>
+        <returns>An <see cref="T:System.Collections.IEnumerator" /> for the <see cref="T:System.Net.WebHeaderCollection" />.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>