stomp out some unused code in FFMPEG path determination

BizHawk.Client.Common/config/Config.cs

@@ -52,8 +52,6 @@ namespace BizHawk.Client.Common
 		// BIOS Paths
 		public Dictionary<string, string> FirmwareUserSpecifications = new Dictionary<string, string>(); // key: sysid+firmwareId; value: absolute path
 
-		public string FFMpegPath = "%exe%/dll/ffmpeg.exe";
-
 		// General Client Settings
 		public int Input_Hotkey_OverrideOptions = 0;
 		public bool StackOSDMessages = true;

BizHawk.Client.EmuHawk/MainForm.cs

@@ -110,8 +110,6 @@ namespace BizHawk.Client.EmuHawk
 
 			_throttle = new Throttle();
 
-			FFMpeg.FFMpegPath = PathManager.MakeProgramRelativePath(Global.Config.FFMpegPath);
-
 			Global.CheatList = new CheatCollection();
 			Global.CheatList.Changed += ToolHelpers.UpdateCheatRelatedTools;