Using cleanup

PerfectNumbers.Core/Cpu/FactorCacheLease.cs

@@ -1,5 +1,3 @@
-using System.Collections.Generic;
-
 namespace PerfectNumbers.Core.Cpu;
 
 internal struct FactorCacheLease

PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs

@@ -1,5 +1,3 @@
-using System;
-
 namespace PerfectNumbers.Core.Cpu;
 
 internal sealed class MersenneCpuDivisorScanSession : IMersenneNumberDivisorByDivisorTester.IDivisorScanSession

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs

@@ -1,5 +1,3 @@
-using System;
-using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using PerfectNumbers.Core.Gpu;