Supress compiler warning

I don't think this is a sustainable solution if we start doing this in more places.

osu.Game/Screens/Tournament/ScrollingTeamContainer.cs

@@ -28,7 +28,11 @@ public class ScrollingTeamContainer : Container
 
         private readonly Container tracker;
 
+#pragma warning disable 649
+        // set via reflection.
         private float speed;
+#pragma warning restore 649
+
         private int expiredCount;
 
         private float offset;