misc: chore: Remove unnecessary usings

src/Ryujinx.Cpu/LightningJit/Cache/JitCacheInvalidation.cs

@@ -1,5 +1,4 @@
 using ARMeilleure.Memory;
-using System;
 using System.Runtime.InteropServices;
 
 namespace Ryujinx.Cpu.LightningJit.Cache

src/Ryujinx.Cpu/LightningJit/Cache/JitSupportDarwin.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Runtime.InteropServices;
 using System.Runtime.Versioning;