Upgrade FluentAssertions package to v6.8.0

Author: YevgeniyShunevych

test/Atata.Configuration.Json.Tests/Atata.Configuration.Json.Tests.csproj

@@ -15,7 +15,7 @@
 
   <ItemGroup>
     <PackageReference Include="Atata.WebDriverSetup" Version="2.4.0" />
-    <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="NLog" Version="5.0.4" />
     <PackageReference Include="NUnit" Version="3.13.3" />