build(deps): bump Microsoft.ProjectReunion from 0.8.3 to 0.8.4 in /src (

#2938)

Bumps [Microsoft.ProjectReunion](https://github.com/microsoft/projectreunion) from 0.8.3 to 0.8.4.
- [Release notes](https://github.com/microsoft/projectreunion/releases)
- [Commits](https://github.com/microsoft/projectreunion/commits)

---
updated-dependencies:
- dependency-name: Microsoft.ProjectReunion
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

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

src/ReactiveUI.WinUI/ReactiveUI.WinUI.csproj

@@ -11,7 +11,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.ProjectReunion" Version="0.8.3" />
+    <PackageReference Include="Microsoft.ProjectReunion" Version="0.8.4" />
   </ItemGroup>
 
   <ItemGroup>