Avalonia: Add macOS check for Color Space Passthrough (#5754)

* add macOS check for color passthrough

* use existing IsMacOS property

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Co-authored-by: jcm <butt@butts.com>

src/Ryujinx.Ava/UI/ViewModels/SettingsViewModel.cs

@@ -147,6 +147,7 @@ namespace Ryujinx.Ava.UI.ViewModels
         public bool EnableTextureRecompression { get; set; }
         public bool EnableMacroHLE { get; set; }
         public bool EnableColorSpacePassthrough { get; set; }
+        public bool ColorSpacePassthroughAvailable => IsMacOS;
         public bool EnableFileLog { get; set; }
         public bool EnableStub { get; set; }
         public bool EnableInfo { get; set; }