Bump Swashbuckle.AspNetCore.SwaggerUi in /src/FlubuCore.WebApi

Bumps [Swashbuckle.AspNetCore.SwaggerUi](https://github.com/domaindrivendev/Swashbuckle.AspNetCore) from 4.0.1 to 6.4.0.
- [Release notes](https://github.com/domaindrivendev/Swashbuckle.AspNetCore/releases)
- [Commits](domaindrivendev/Swashbuckle.AspNetCore@v4.0.1...v6.4.0)

---
updated-dependencies:
- dependency-name: Swashbuckle.AspNetCore.SwaggerUi
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

src/FlubuCore.WebApi/FlubuCore.WebApi.csproj

@@ -92,7 +92,7 @@
     </PackageReference>
     <PackageReference Include="Swashbuckle.AspNetCore.Annotations" Version="4.0.1" />
     <PackageReference Include="Swashbuckle.AspNetCore.SwaggerGen" Version="4.0.1" />
-    <PackageReference Include="Swashbuckle.AspNetCore.SwaggerUi" Version="4.0.1" />
+    <PackageReference Include="Swashbuckle.AspNetCore.SwaggerUi" Version="6.4.0" />
     <PackageReference Include="MailKit" Version="2.6.0" />
     <PackageReference Include="Serilog.Extensions.Logging.File" Version="2.0.0" />
   </ItemGroup>