Bump FluentAssertions from 6.4.0 to 8.6.0#2230

dependabot[bot] wants to merge 1 commit intomaindotnet/reactive:mainfrom

dependabot/nuget/Ix.NET/Source/System.Interactive.Async.Providers.Tests/multi-60cd6c56ebdotnet/reactive:dependabot/nuget/Ix.NET/Source/System.Interactive.Async.Providers.Tests/multi-60cd6c56ebCopy head branch name to clipboard