fix some usings

src/BizHawk.Bizware.Input/KeyInput/QuartzKeyInput.cs

@@ -1,6 +1,5 @@
 #nullable enable
 
-using System;
 using System.Collections.Generic;
 
 using BizHawk.Client.Common;

src/BizHawk.Common/macOS/QuartzImports.cs

@@ -1,6 +1,5 @@
 #nullable enable
 
-using System;
 using System.Runtime.InteropServices;
 
 namespace BizHawk.Common

src/BizHawk.Emulation.Cores/Consoles/WonderSwan/WonderSwan.IStatable.cs

@@ -1,11 +1,10 @@
 using System;
 using System.IO;
+using System.Runtime.InteropServices;
+
 using Newtonsoft.Json;
 
-using BizHawk.Common;
 using BizHawk.Emulation.Common;
-using System.Runtime.InteropServices;
-using BizHawk.Common.IOExtensions;
 
 namespace BizHawk.Emulation.Cores.WonderSwan
 {