Fix to issue #4316 - error in duration to frequency calculation.

Author: Pete Ansell

Microsoft.Toolkit.Uwp.Input.GazeInteraction/OneEuroFilter.cs

@@ -57,7 +57,7 @@ public virtual GazeFilterArgs Update(GazeFilterArgs args)
             Point cutoff = new Point(cf, cf);
 
             // determine sampling frequency based on last time stamp
-            float samplingFrequency = 100000000.0f / Math.Max(1, (args.Timestamp - _lastTimestamp).Ticks);
+            var samplingFrequency = (float)TimeSpan.TicksPerSecond / Math.Max(1, (args.Timestamp - _lastTimestamp).Ticks);
             _lastTimestamp = args.Timestamp;
 
             // calculate change in distance...