build(deps): bump ReactiveUI.Testing from 14.3.1 to 16.2.6 (#17)

Bumps [ReactiveUI.Testing](https://github.com/reactiveui/reactiveui) from 14.3.1 to 16.2.6.
- [Release notes](https://github.com/reactiveui/reactiveui/releases)
- [Commits](reactiveui/ReactiveUI@14.3.1...16.2.6)

---
updated-dependencies:
- dependency-name: ReactiveUI.Testing
  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>

Author: dependabot[bot]

src/ReactiveMarbles.CacheDatabase.Tests/ReactiveMarbles.CacheDatabase.Tests.csproj

@@ -21,7 +21,7 @@
     <PackageReference Include="PublicApiGenerator" Version="10.2.0" />
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
-    <PackageReference Include="ReactiveUI.Testing" Version="14.3.1" />
+    <PackageReference Include="ReactiveUI.Testing" Version="16.2.6" />
   </ItemGroup>
 
   <ItemGroup>