Update NuGet source URL in publish workflow

Changed the NuGet package publishing command in `nuget-publish.yml` to use the correct source URL `https://api.nuget.org/v3/index.json`. The `-s` flag replaces `--source`, while retaining the `--skip-duplicate` option to prevent duplicate package pushes.

.github/workflows/nuget-publish.yml

@@ -60,5 +60,5 @@ jobs:
         run: |
           for f in ./nupkgs/*.nupkg
           do
-            dotnet nuget push $f --api-key ${{secrets.NUGET_API_KEY}} --source https://api.nupkg.org/v3/index.json --skip-duplicate
+            dotnet nuget push $f --api-key ${{secrets.NUGET_API_KEY}} -s https://api.nuget.org/v3/index.json --skip-duplicate
           done