fix: remove double entry '@azure/functions' package

Sending the PR according to the issue mentioned by @dfberry

Remember that, to reproduce, go to the folder: api-v4. Inside the folder, create a file called: local.settings.json and put the following code:

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "node",
    "AzureWebJobsFeatureFlags": "EnableWorkerIndexing"
  }
}

Then type the command: npm i && npm start. You will see the list of APIs created in this new version. To test, click on "Open in Browser."

And then include in the end of the url: <codespaces-url>/api/listings

Azure-Samples / contoso-real-estate