build(deps): bump FluentAssertions from 6.8.0 to 6.9.0 in /src (#830)

Bumps [FluentAssertions](https://github.com/fluentassertions/fluentassertions) from 6.8.0 to 6.9.0.
- [Release notes](https://github.com/fluentassertions/fluentassertions/releases)
- [Changelog](https://github.com/fluentassertions/fluentassertions/blob/develop/AcceptApiChanges.ps1)
- [Commits](fluentassertions/fluentassertions@6.8.0...6.9.0)

---
updated-dependencies:
- dependency-name: FluentAssertions
  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>

src/Akavache.Tests/Akavache.Tests.csproj

@@ -18,7 +18,7 @@
     <PackageReference Include="ReactiveUI.Testing" Version="18.*" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="SQLitePCLRaw.bundle_e_sqlite3" Version="2.1.4" />
-    <PackageReference Include="FluentAssertions" Version="6.8.0" />
+    <PackageReference Include="FluentAssertions" Version="6.9.0" />
     <PackageReference Include="DiffEngine" Version="11.1.0" />
     <PackageReference Include="PublicApiGenerator" Version="10.3.0" />
     <PackageReference Include="coverlet.msbuild" Version="3.2.0">