Remove IEmuClientApi.RunningSystem from the API

other code in EmuClientApi (the impl.) uses this prop, so it's staying for now

src/BizHawk.Client.Common/Api/Interfaces/IEmuClientApi.cs

@@ -7,8 +7,6 @@ namespace BizHawk.Client.Common
 {
 	public interface IEmuClientApi : IExternalApi
 	{
-		SystemInfo RunningSystem { get; }
-
 		/// <summary>
 		/// Occurs before a quickload is done (just after user has pressed the shortcut button
 		/// or has click on the item menu)

src/BizHawk.Client.EmuHawk/Api/ClientApi.cs

@@ -8,9 +8,6 @@ namespace BizHawk.Client.EmuHawk
 {
 	public static class ClientApi
 	{
-		/// <inheritdoc cref="IEmuClientApi.DoFrameAdvance"/>
-		public static SystemInfo RunningSystem => GlobalWin.ClientApi.RunningSystem;
-
 		/// <inheritdoc cref="IEmuClientApi.BeforeQuickLoad"/>
 		public static event BeforeQuickLoadEventHandler BeforeQuickLoad
 		{

src/BizHawk.Client.EmuHawk/Api/Libraries/EmuClientApi.cs

@@ -39,7 +39,8 @@ namespace BizHawk.Client.EmuHawk
 
 		private readonly JoypadStringToEnumConverter JoypadConverter = new JoypadStringToEnumConverter();
 
-		public SystemInfo RunningSystem
+		/// <remarks>future humans: if this is broken, rewrite the caller instead if fixing it</remarks>
+		private SystemInfo RunningSystem
 		{
 			get
 			{
@@ -54,7 +55,7 @@ namespace BizHawk.Client.EmuHawk
 							_ => throw new ArgumentOutOfRangeException()
 						};
 					case "PCE":
-						return SystemInfo.PCE; // not always accurate, but anyone wanting accuracy has probably figured out how to use IEmu.GetSystemId()
+						return SystemInfo.PCE;
 					case "SMS":
 						var sms = (SMS) Emulator;
 						return sms.IsSG1000