[FEATURE] Implement Llama model provider structued_output

[Unshure]

Problem Statement

The recently added structured_output feature was not able to test against the Llama model provider since we did not have an api key available to test the feature with.

Proposed Solution

Uncomment and test the code to ensure structured output works for the Llama model provider: https://github.com/strands-agents/sdk-python/blob/main/src/strands/models/llamaapi.py#L405-L416

Use Case

Producing structured output when calling a Llama model

Alternatives Solutions

N/A

Additional Context

N/A