Using cleanup

PerfectNumbers.Core/MersenneDivisorCycles.cs

@@ -1,11 +1,9 @@
 using System.Buffers;
 using System.Buffers.Binary;
-using System.Collections.Generic;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Security.Cryptography;
 using System.Text;
-using System.Threading;
 using PerfectNumbers.Core.Gpu;
 using ILGPU;
 using ILGPU.Runtime;