Bump ReactiveUI.Events.WPF and System.Reactive

Bumps [ReactiveUI.Events.WPF](https://github.com/reactiveui/reactiveui) and [System.Reactive](https://github.com/dotnet/reactive). These dependencies needed to be updated together.

Updates `ReactiveUI.Events.WPF` from 13.2.18 to 15.1.1
- [Release notes](https://github.com/reactiveui/reactiveui/releases)
- [Commits](reactiveui/ReactiveUI@13.2.18...15.1.1)

Updates `System.Reactive` from 5.0.0 to 5.0.0
- [Release notes](https://github.com/dotnet/reactive/releases)
- [Commits](dotnet/reactive@ixnet-v5.0.0...ixnet-v5.0.0)

---
updated-dependencies:
- dependency-name: ReactiveUI.Events.WPF
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: System.Reactive
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Shadowsocks.WPF/Shadowsocks.WPF.csproj

@@ -52,7 +52,7 @@
     <PackageReference Include="MaterialDesignThemes" Version="4.0.0" />
     <PackageReference Include="MdXaml" Version="1.10.0" />
     <PackageReference Include="OxyPlot.Wpf" Version="2.0.0" />
-    <PackageReference Include="ReactiveUI.Events.WPF" Version="13.2.18" />
+    <PackageReference Include="ReactiveUI.Events.WPF" Version="15.1.1" />
     <PackageReference Include="ReactiveUI.Fody" Version="13.2.18" />
     <PackageReference Include="ReactiveUI.Validation" Version="2.1.1" />
     <PackageReference Include="ReactiveUI.WPF" Version="13.2.18" />