Bump FluentAssertions from 6.11.0 to 6.12.0 in /src (#150)

Bumps [FluentAssertions](https://github.com/fluentassertions/fluentassertions) from 6.11.0 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@6.11.0...6.12.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/BBT.StructureTools.Tests/BBT.StructureTools.Tests.csproj

@@ -32,7 +32,7 @@
     <PackageReference Include="xunit.runner.visualstudio" Version="2.5.0">
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="FluentAssertions" Version="6.11.0">
+    <PackageReference Include="FluentAssertions" Version="6.12.0">
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" Version="3.3.2">