Remove unused prop from a MainForm interface

fixes 62537118a

src/BizHawk.Client.EmuHawk/IEmuHawkMainFormToApi.cs

@@ -36,9 +36,6 @@ namespace BizHawk.Client.EmuHawk
 		/// <remarks>only referenced from <see cref="EmuClientApi"/></remarks>
 		bool PauseAvi { set; }
 
-		/// <remarks>only referenced from <see cref="EmuClientApi"/></remarks>
-		PresentationPanel PresentationPanel { get; }
-
 		void AddOnScreenMessage(string message);
 
 		/// <remarks>only referenced from <see cref="EmuClientApi"/></remarks>

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -1552,7 +1552,7 @@ namespace BizHawk.Client.EmuHawk
 		// input state which has been destined for client hotkey consumption are colesced here
 		private readonly InputCoalescer _hotkeyCoalescer = new InputCoalescer();
 
-		public PresentationPanel PresentationPanel { get; }
+		private readonly PresentationPanel PresentationPanel;
 
 		// countdown for saveram autoflushing
 		public int AutoFlushSaveRamIn { get; set; }