build(deps): bump ReactiveUI from 18.4.44 to 19.2.1 in /src (#1020)

Bumps [ReactiveUI](https://github.com/reactiveui/reactiveui) from 18.4.44 to 19.2.1.
- [Release notes](https://github.com/reactiveui/reactiveui/releases)
- [Commits](reactiveui/ReactiveUI@18.4.44...19.2.1)

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

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

src/ReactiveUI.DI.Tests/ReactiveUI.DI.Tests.csproj

@@ -28,7 +28,7 @@
   </Choose>
 
   <ItemGroup>
-    <PackageReference Include="ReactiveUI" Version="18.4.44" />
+    <PackageReference Include="ReactiveUI" Version="19.2.1" />
   </ItemGroup>
 
   <ItemGroup>