Bump FluentAssertions from 6.11.0 to 6.12.0 in /GraphEngine.Tests (#82)

Bumps [FluentAssertions](https://github.com/fluentassertions/fluentassertions) from 6.11.0 to 6.12.0.
- [Release notes](https://github.com/fluentassertions/fluentassertions/releases)
- [Changelog](https://github.com/fluentassertions/fluentassertions/blob/develop/AcceptApiChanges.ps1)
- [Commits](fluentassertions/fluentassertions@6.11.0...6.12.0)

---
updated-dependencies:
- dependency-name: FluentAssertions
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

GraphEngine.Tests/GraphEngine.Tests.csproj

@@ -9,7 +9,7 @@
   <ItemGroup>
     <PackageReference Include="dotNetRDF" Version="3.0.1" />
     <PackageReference Include="ExpressionTreeToolkit.Core" Version="0.4.0" />
-    <PackageReference Include="FluentAssertions" Version="6.11.0" />
+    <PackageReference Include="FluentAssertions" Version="6.12.0" />
     <PackageReference Include="coverlet.collector" Version="6.0.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>