Bump FluentAssertions from 6.7.0 to 6.8.0

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] <support@github.com>

src/Akka.Quartz.Actor.Tests/Akka.Quartz.Actor.Tests.csproj

@@ -9,7 +9,7 @@
     <PackageReference Include="xunit.runner.visualstudio" Version="$(XunitRunnerVersion)" />
     <PackageReference Include="xunit" Version="$(XunitVersion)" />
     <PackageReference Include="Akka.TestKit.Xunit2" Version="$(AkkaVersion)" />
-    <PackageReference Include="FluentAssertions" Version="6.7.0" />
+    <PackageReference Include="FluentAssertions" Version="6.8.0" />
     <PackageReference Include="Quartz" Version="$(QuartzVersion)" />
   </ItemGroup>