Bump Microsoft.OpenApi from 1.6.11 to 1.6.12 in /src

Bumps [Microsoft.OpenApi](https://github.com/Microsoft/OpenAPI.NET) from 1.6.11 to 1.6.12.
- [Release notes](https://github.com/Microsoft/OpenAPI.NET/releases)
- [Commits](microsoft/OpenAPI.NET@1.6.11...1.6.12)

---
updated-dependencies:
- dependency-name: Microsoft.OpenApi
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

src/IoTHub.Portal.Server/IoTHub.Portal.Server.csproj

@@ -62,7 +62,7 @@
     </PackageReference>
     <PackageReference Include="Microsoft.Extensions.Http.Polly" Version="7.0.15" />
     <PackageReference Include="Microsoft.Graph" Version="5.38.0" />
-    <PackageReference Include="Microsoft.OpenApi" Version="1.6.11" />
+    <PackageReference Include="Microsoft.OpenApi" Version="1.6.12" />
     <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.19.6" />
     <PackageReference Include="Microsoft.Identity.Web.UI" Version="2.15.3" />
     <PackageReference Include="MudBlazor" Version="6.11.0" />