Remove imports no longer used after recent changes

src/BizHawk.Client.EmuHawk/config/NES/NESSyncSettingsForm.cs

@@ -1,7 +1,5 @@
 using System;
-using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Windows.Forms;
 
 using BizHawk.Client.Common;

src/BizHawk.Client.EmuHawk/tools/HexEditor/HexFind.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Drawing;
-using System.Text;
 using System.Windows.Forms;
 
 using BizHawk.Common.BufferExtensions;

src/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/NES.Core.cs

@@ -1,7 +1,6 @@
 // NOTE: to match Mesen timings, set idleSynch to true at power on, and set start_up_offset to -3
 
 using System;
-using System.Linq;
 
 using BizHawk.Common;
 using BizHawk.Emulation.Common;