build(deps): Bump ReactiveUI.Testing from 18.2.9 to 18.3.1 (#102)

Bumps [ReactiveUI.Testing](https://github.com/reactiveui/reactiveui) from 18.2.9 to 18.3.1.
- [Release notes](https://github.com/reactiveui/reactiveui/releases)
- [Commits](reactiveui/ReactiveUI@18.2.9...18.3.1)

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

Author: dependabot[bot]

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

@@ -20,7 +20,7 @@
     </PackageReference>
     <PackageReference Include="FluentAssertions" Version="6.7.0" />
     <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
-    <PackageReference Include="ReactiveUI.Testing" Version="18.2.5" />
+    <PackageReference Include="ReactiveUI.Testing" Version="18.3.1" />
   </ItemGroup>
 
   <ItemGroup>

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

@@ -19,7 +19,7 @@
     </PackageReference>
     <PackageReference Include="FluentAssertions" Version="6.7.0" />
     <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
-    <PackageReference Include="ReactiveUI.Testing" Version="18.2.9" />
+    <PackageReference Include="ReactiveUI.Testing" Version="18.3.1" />
   </ItemGroup>
 
   <ItemGroup>