Update LibManSample.csproj

Update LibMan restore instructions to a much more recent version.

Author: jzabroski

aspnetcore/client-side/libman/samples/LibManSample/LibManSample.csproj

@@ -8,7 +8,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.App" />
     <!-- <snippet_RestoreOnBuildPackage> -->
-    <PackageReference Include="Microsoft.Web.LibraryManager.Build" Version="1.0.113" />
+    <PackageReference Include="Microsoft.Web.LibraryManager.Build" Version="3.0.71" />
     <!-- </snippet_RestoreOnBuildPackage> -->
   </ItemGroup>