Reduce dependencies

csharp/ProtocolBuffers.Test/ProtocolBuffers.Test.csproj

@@ -42,8 +42,6 @@
       <HintPath>lib\Rhino.Mocks.dll</HintPath>
     </Reference>
     <Reference Include="System" />
-    <Reference Include="System.Data" />
-    <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="AbstractMessageTest.cs" />