Fix GlyphRun.GetTralingWhitespaceLengthRightToLeft
Fix GlyphRun.GetTralingWhitespaceLengthRightToLeft

AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia