Update MultipartContent.xml

Typo: Change HHTP to HTTP

Author: khejd

xml/System.Net.Http/MultipartContent.xml

@@ -653,7 +653,7 @@ This member is an explicit interface member implementation. It can be used only
         <Parameter Name="length" Type="System.Int64" RefType="out" />
       </Parameters>
       <Docs>
-        <param name="length">The length in bytes of the HHTP content.</param>
+        <param name="length">The length in bytes of the HTTP content.</param>
         <summary>Determines whether the HTTP multipart content has a valid length in bytes.</summary>
         <returns>
           <see langword="true" /> if <paramref name="length" /> is a valid length; otherwise, <see langword="false" />.</returns>