Force tournament client to run in windowed mode

We generally haven't tested in other modes, and it doesn't really make
sense as you wouldn't be able to use it in a meaningful way otherwise.

- [ ] Test on windows.

osu.Game.Tournament/TournamentGame.cs

@@ -31,6 +31,7 @@ public class TournamentGame : TournamentGameBase
         public static readonly Color4 TEXT_COLOUR = Color4Extensions.FromHex("#fff");
         private Drawable heightWarning;
         private Bindable<Size> windowSize;
+        private Bindable<WindowMode> windowMode;
 
         [BackgroundDependencyLoader]
         private void load(FrameworkConfigManager frameworkConfig)
@@ -43,6 +44,12 @@ private void load(FrameworkConfigManager frameworkConfig)
                 heightWarning.Alpha = size.NewValue.Width < minWidth ? 1 : 0;
             }), true);
 
+            windowMode = frameworkConfig.GetBindable<WindowMode>(FrameworkSetting.WindowMode);
+            windowMode.BindValueChanged(mode => ScheduleAfterChildren(() =>
+            {
+                windowMode.Value = WindowMode.Windowed;
+            }), true);
+
             AddRange(new[]
             {
                 new Container