Don't include STIUtilties.cs until it is required by a test area.

Author: ryalanms

src/Test/Infra/Drivers/STI/Sti.csproj

@@ -10,7 +10,9 @@
  <ItemGroup>
     <Compile Include="SimpleTestInvoke.cs" />
     <Compile Include="StiDriverParameters.cs" />
+    <!-- 
     <Compile Include="StiUtilities.cs" />
+    -->
   </ItemGroup>
 
   <ItemGroup>