chore(deps): update dependency reactiveui.wpf to v20

Author: renovate[bot]

src/Camelotia.Presentation.Wpf/Camelotia.Presentation.Wpf.csproj

@@ -13,7 +13,7 @@
     <PackageReference Include="MaterialDesignColors" Version="3.1.0" />
     <PackageReference Include="MaterialDesignThemes" Version="5.1.0" />
     <PackageReference Include="MaterialDesignThemes.MahApps" Version="3.1.0" />
-    <PackageReference Include="ReactiveUI.WPF" Version="18.4.44" />
+    <PackageReference Include="ReactiveUI.WPF" Version="20.3.1" />
     <PackageReference Include="ReactiveMarbles.ObservableEvents.SourceGenerator" Version="1.3.1" PrivateAssets="all" />
   </ItemGroup>
   <ItemGroup>