Fix official build by resolving conflict when building the docs transport package

Author: joperezr

src/Packages/Microsoft.Internal.Extensions.DotNetApiDocs.Transport/Microsoft.Internal.Extensions.DotNetApiDocs.Transport.proj

@@ -27,6 +27,10 @@
       Private="false"
       Include="$(SrcLibrariesDir)\*\*.*proj"
       Exclude="$(MSBuildProjectFullPath)" />
+
+    <!-- This is needed in order to avoid a version conflict between some dependencies bringing in the 6.0 version of the assembly
+    and some others depending on the 9.0 version. -->
+    <PackageReference Include="System.Text.Encodings.Web" />
   </ItemGroup>
 
   <!-- Include the reference assembly and put the documentation file next to it. -->