Add version to PackageRef in non-SDK style project assets

Author: zivkan

test/TestAssets/TestProjects/DesktopAppWithLibrary-NonSDK/TestApp/TestApp.csproj

@@ -44,7 +44,7 @@
     <Compile Include="**\*.cs" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" />
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 

test/TestAssets/TestProjects/DesktopAppWithLibrary-PackagesConfig/TestApp/TestApp.csproj

@@ -98,7 +98,7 @@
     <None Include="packages.config" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" />
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" version="1.0.3" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it.