Use native `OpenFolderDialog` in GUI

DiscordChatExporter.Gui/DiscordChatExporter.Gui.csproj

@@ -21,7 +21,6 @@
     <PackageReference Include="MaterialDesignColors" Version="2.1.4" />
     <PackageReference Include="MaterialDesignThemes" Version="4.9.0" />
     <PackageReference Include="Microsoft.Xaml.Behaviors.Wpf" Version="1.1.77" />
-    <PackageReference Include="Ookii.Dialogs.Wpf" Version="5.0.1" />
     <PackageReference Include="Onova" Version="2.6.10" />
     <PackageReference Include="PropertyChanged.Fody" Version="4.1.0" PrivateAssets="all" />
     <PackageReference Include="Stylet" Version="1.3.6" />

DiscordChatExporter.Gui/ViewModels/Framework/DialogManager.cs

@@ -4,7 +4,6 @@ using System.Threading;
 using System.Threading.Tasks;
 using MaterialDesignThemes.Wpf;
 using Microsoft.Win32;
-using Ookii.Dialogs.Wpf;
 using Stylet;
 
 namespace DiscordChatExporter.Gui.ViewModels.Framework;
@@ -68,9 +67,8 @@ public class DialogManager : IDisposable
 
     public string? PromptDirectoryPath(string defaultDirPath = "")
     {
-        var dialog = new VistaFolderBrowserDialog { SelectedPath = defaultDirPath };
-
-        return dialog.ShowDialog() == true ? dialog.SelectedPath : null;
+        var dialog = new OpenFolderDialog { InitialDirectory = defaultDirPath };
+        return dialog.ShowDialog() == true ? dialog.FolderName : null;
     }
 
     public void Dispose()