Remove unused usings

Blueberry/App.xaml.cs

@@ -1,5 +1,4 @@
-using Blueberry;
-using Blueberry.Redmine;
+using Blueberry.Redmine;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;

Blueberry/MainWindow.xaml.cs

@@ -4,7 +4,6 @@ using Blueberry.Redmine.Dto;
 using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.Text.RegularExpressions;
-using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Input;
 using Wpf.Ui.Controls;

Blueberry/UpdateManager.cs

@@ -2,7 +2,6 @@
 using System.IO;
 using System.Net.Http;
 using System.Text.Json;
-using Windows.Media.Protection.PlayReady;
 
 namespace Blueberry
 {