Bump FluentAssertions from 6.12.0 to 8.7.1

---
updated-dependencies:
- dependency-name: FluentAssertions
  dependency-version: 8.7.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

test/Dan.Plugin.Sjofart.Test/Dan.Plugin.Sjofart.Test.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="6.12.0" />
+    <PackageReference Include="FluentAssertions" Version="8.7.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
     <PackageReference Include="Moq" Version="4.17.2" />
     <PackageReference Include="xunit" Version="2.9.3" />