build(deps): bump ReactiveUI.Uwp from 17.1.50 to 18.2.5 in /samples

Bumps [ReactiveUI.Uwp](https://github.com/reactiveui/reactiveui) from 17.1.50 to 18.2.5.
- [Release notes](https://github.com/reactiveui/reactiveui/releases)
- [Commits](reactiveui/ReactiveUI@17.1.50...18.2.5)

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

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

Author: dependabot[bot]

samples/LoginApp.Uwp/LoginApp.Uwp.csproj

@@ -151,7 +151,7 @@
     <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform" Version="6.2.13" />
     <PackageReference Include="ReactiveUI" Version="17.*" />
     <PackageReference Include="ReactiveUI.Uwp">
-      <Version>17.1.50</Version>
+      <Version>18.2.5</Version>
     </PackageReference>
     <PackageReference Include="ReactiveUI.Validation" Version="2.*" />
   </ItemGroup>