build(deps): bump FluentAssertions from 7.0.0 to 8.1.0

Bumps [FluentAssertions](https://github.com/fluentassertions/fluentassertions) from 7.0.0 to 8.1.0.
- [Release notes](https://github.com/fluentassertions/fluentassertions/releases)
- [Changelog](https://github.com/fluentassertions/fluentassertions/blob/main/AcceptApiChanges.ps1)
- [Commits](fluentassertions/fluentassertions@7.0.0...8.1.0)

---
updated-dependencies:
- dependency-name: FluentAssertions
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

tests/Atypical.VirtualFileSystem.UnitTests/Atypical.VirtualFileSystem.UnitTests.csproj

@@ -6,7 +6,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="FluentAssertions" Version="7.0.0" />
+        <PackageReference Include="FluentAssertions" Version="8.1.0" />
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
         <PackageReference Include="xunit" Version="2.9.2" />
         <PackageReference Include="xunit.runner.visualstudio" Version="3.0.0">