Update MetroProgressBar.cs

Occur Warning 6 in MetroProgressBar

If excute MetroProgressBar, as below, ouput debug.

System.Windows.Media.Animation Warning: 6 : Unable to perform action because the specified Storyboard was never applied to this object for interactive control.; Action='Remove'; Storyboard='System.Windows.Media.Animation.Storyboard'; Storyboard.HashCode='12083158'; Storyboard.Type='System.Windows.Media.Animation.Storyboard'; TargetElement='System.Windows.Media.Animation.Storyboard'; TargetElement.HashCode='12083158'; TargetElement.Type='System.Windows.Media.Animation.Storyboard'

Solution, delete "indeterminate.Storyboard.Remove();"