Fix required llama-cpp-agent version

[dinerburger]

The Get Keywords node fails as llama-cpp-agent has refactored structured output. This moves back to a pre-April 29 2024 version to ensure the API is the expected one.

[gokayfem]

Locking this version can cause locking some libraries it is depending. I am not sure about doing this. I want VLM nodes to be version free. It is better to fix the node instead of locking the version.

[dinerburger]

I did try; wasn't sure how to send grammar down, though the temperature setting went into the sampling_settings field okay.

[Mister-Link]

Definitely broken for several nodes (anything that uses "temperature" as a parameter, in my case). There's no alternative to dinerburger's fix:

pip uninstall llama-cpp-agent
pip install llama-cpp-agent==0.0.26