Bump ReactiveUI from 19.2.1 to 19.4.1 in /src (#100)

Bumps [ReactiveUI](https://github.com/reactiveui/reactiveui) from 19.2.1 to 19.4.1.
- [Release notes](https://github.com/reactiveui/reactiveui/releases)
- [Commits](reactiveui/ReactiveUI@19.2.1...19.4.1)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/ReactiveUI.Uno/ReactiveUI.Uno.csproj

@@ -27,6 +27,6 @@
 
   <ItemGroup>
     <PackageReference Include="Uno.UI" Version="4.9.26" />
-    <PackageReference Include="ReactiveUI" Version="19.2.1" />
+    <PackageReference Include="ReactiveUI" Version="19.4.1" />
   </ItemGroup>
 </Project>