03-integrations - [Bug] EntraID_and_3LO_Outbound_for_Tools-Failed to retrieve token

The bug occurs in below sample notebook.
https://github.com/awslabs/amazon-bedrock-agentcore-samples/blob/main/03-integrations/IDP-examples/EntraID/Step_by_Step_Entra_ID_with_AgentCore_Gateway.ipynb

**Bug Description**
After executing `id_token = need_access_token(access_token="")` and successfully logging into EntraID with the correct credentials, the browser displays the following error:
```
{
"fieldList": null,
"message": "Failed to retrieve token",
"reason": null
}
```

Start with 03-integrations/IDP-examples/EntraID/Step_by_Step_Entra_ID_with_AgentCore_Gateway.ipynb and reproduce the `need_access_token(access_token="")` call after signing in to EntraID. Trace why the notebook displays "Failed to retrieve token"; done means the sample retrieves the token successfully with valid credentials.

Written by the indexing model from the issue text.