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>

Author: dependabot[bot]

test/Microsoft.OpenApi.Readers.Tests/Microsoft.OpenApi.Readers.Tests.csproj

@@ -251,7 +251,7 @@
 
     <ItemGroup>
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
-        <PackageReference Include="FluentAssertions" Version="6.7.0">
+        <PackageReference Include="FluentAssertions" Version="6.8.0">
         </PackageReference>
         <PackageReference Include="Newtonsoft.Json" Version="13.0.2-beta1">
         </PackageReference>

test/Microsoft.OpenApi.Tests/Microsoft.OpenApi.Tests.csproj

@@ -15,7 +15,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="6.7.0" />
+    <PackageReference Include="FluentAssertions" Version="6.8.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
     <PackageReference Include="Moq" Version="4.18.2" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />