build(deps): update FluentAssertions requirement from 6.11.* to 6.12.*

Updates the requirements on [FluentAssertions](https://github.com/fluentassertions/fluentassertions) to permit the latest version.
- [Release notes](https://github.com/fluentassertions/fluentassertions/releases)
- [Changelog](https://github.com/fluentassertions/fluentassertions/blob/develop/AcceptApiChanges.ps1)
- [Commits](fluentassertions/fluentassertions@6.11.0...6.12.0)

---
updated-dependencies:
- dependency-name: FluentAssertions
  dependency-type: direct:production
...

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

grate.unittests/grate.unittests.csproj

@@ -15,7 +15,7 @@
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.Data.SqlClient" Version="5.1.*" />
-    <PackageReference Include="FluentAssertions" Version="6.11.*" />
+    <PackageReference Include="FluentAssertions" Version="6.12.*" />
     <PackageReference Include="NSubstitute" Version="5.0.*" />
     <PackageReference Include="Dapper" Version="2.0.*" />
     <PackageReference Include="Oracle.ManagedDataAccess.Core" Version="3.21.*" />