Bump FluentAssertions from 6.7.0 to 6.8.0 (#1947)

Bumps [FluentAssertions](https://github.com/fluentassertions/fluentassertions) from 6.7.0 to 6.8.0.
- [Release notes](https://github.com/fluentassertions/fluentassertions/releases)
- [Changelog](https://github.com/fluentassertions/fluentassertions/blob/develop/AcceptApiChanges.ps1)
- [Commits](fluentassertions/fluentassertions@6.7.0...6.8.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

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

Author: dependabot[bot]

test/Directory.Build.props

@@ -15,7 +15,7 @@
     <ItemGroup>
         <PackageReference Include="xunit" Version="2.4.2"/>
         <PackageReference Include="AutoFixture" Version="4.17.0"/>
-        <PackageReference Include="FluentAssertions" Version="6.7.0"/>
+        <PackageReference Include="FluentAssertions" Version="6.8.0"/>
     </ItemGroup>
     <ItemGroup Condition="$(TargetFramework) == 'net472'">
         <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies.net472" Version="1.0.3" PrivateAssets="All"/>