Fix key to request personality when creating a session

[ManueleSigona]

Proposed Changes

This PR fixes a bug: the key to use a specific personality in the request payload for the API to create a session is currently set to requestModel, while it should be requestedModel. This causes the personality string that we pass to be silently ignored. You can see for example that passing "next-gen" will always start a session with the "talkative-01" personality.

Linked Issues

n.a.

Types of changes

• Bug fix (non-breaking change that fixes an issue).
• New feature added (non-breaking change that adds functionality).
• Breaking change (fix or feature that would cause existing functionality to stop working as expected).
• Documentation update.
• Something else (e.g., tests, scripts, example, deployment, infrastructure).

Checklist

• I have read the CONTRIBUTING guide
• Checks and tests pass locally

If applicable

• I have added tests that prove my fix is effective or that my feature works
• I have checked that code coverage does not decrease
• I have added/updated the documentation

Further comments

n.a.