[tests] Add missing file to .NET tests. (#17947)

This fixes an issue in the BundleStructure tests: > error MSB3030: Could not copy the file "/Users/builder/azdo/_work/4/s/xamarin-macios/tests/dotnet/BundleStructure/NoneP.dll" because it was not found.
2023-03-30 18:49:05 +02:00 · 2023-03-30 18:49:05 +02:00 · 2aff5aefe6
--- a/tests/dotnet/BundleStructure/NoneP.dll
+++ b/tests/dotnet/BundleStructure/NoneP.dll