Bump ReactiveUI from 18.3.1 to 18.4.1

Bumps [ReactiveUI](https://github.com/reactiveui/reactiveui) from 18.3.1 to 18.4.1.
- [Release notes](https://github.com/reactiveui/reactiveui/releases)
- [Commits](https://github.com/reactiveui/reactiveui/compare/18.3.1...18.4.1)

---
updated-dependencies:
- dependency-name: ReactiveUI
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

ReactiveExample/ReactiveExample.csproj

@@ -12,7 +12,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="ReactiveUI.Fody" Version="18.3.1" />
-    <PackageReference Include="ReactiveUI" Version="18.3.1" />
+    <PackageReference Include="ReactiveUI" Version="18.4.1" />
     <PackageReference Include="ReactiveMarbles.ObservableEvents.SourceGenerator" Version="1.2.3" PrivateAssets="all" />
   </ItemGroup>
   <ItemGroup>