Bump FluentAssertions from 6.10.0 to 6.12.0

Bumps [FluentAssertions](https://github.com/fluentassertions/fluentassertions) from 6.10.0 to 6.12.0.
- [Release notes](https://github.com/fluentassertions/fluentassertions/releases)
- [Changelog](https://github.com/fluentassertions/fluentassertions/blob/develop/AcceptApiChanges.ps1)
- [Commits](fluentassertions/fluentassertions@6.10.0...6.12.0)

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

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

test/NHSNumberGenerator.Test/NHSNumberGenerator.Test.csproj

@@ -21,7 +21,7 @@
             <PrivateAssets>all</PrivateAssets>
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>
-        <PackageReference Include="FluentAssertions" Version="6.10.0" />
+        <PackageReference Include="FluentAssertions" Version="6.12.0" />
         <PackageReference Include="XunitXml.TestLogger" Version="3.1.11" />
     </ItemGroup>