Cleanup.

src/main/java/de/dennisguse/opentracks/data/TrackDataHub.java

@@ -416,8 +416,7 @@ public class TrackDataHub {
          *
          * @param track the track
          */
-        //TODO Could be @NonNull
-        void onTrackUpdated(Track track);
+        void onTrackUpdated(@NonNull Track track);
 
         /**
          * Called to clear previously-sent track points.

src/main/java/de/dennisguse/opentracks/data/models/Speed.java

@@ -38,15 +38,6 @@ public record Speed(double speed_mps) {
         return speed2;
     }
 
-    public static Speed absDiff(Speed speed1, Speed speed2) {
-        //TODO Why Math.abs? Seems to be a leftover.
-        return Speed.of(Math.abs(speed1.speed_mps - speed2.speed_mps));
-    }
-
-    public Speed mul(double factor) {
-        return new Speed(factor * speed_mps);
-    }
-
     public boolean isZero() {
         return speed_mps == 0;
     }