Update sessionManager.ts - update deprecated model

[gabriellupu]

Update deprecated realtime model as per official notice:

As part of our continuous upgrade process, we are deprecating gpt-4o-realtime-preview-2024-10-01. Access to this model will be shut off on September 10, 2025.

Ahead of the shutdown timeline September 10, we encourage you to switch your model parameter to gpt-4o-realtime-preview-2025-06-03 or gpt-4o-realtime-preview.

The latest model has improved instruction following reliability, tool calling consistency, and interruption behavior of our speech-to-speech model, and introduces a new speed parameter in the API that lets you control how fast the voice speaks during each session. To explore the new version now, specify gpt-4o-realtime-preview-2025-06-03 as the model parameter in the API.