refactor: update ollama models

[sinedied]

Purpose

Update Ollama models used locally for better ones:

• Llama3.1 8B for the chat model
• Nomic Embed for the embeddings (the previously used one now cause context length errors due to Ollama updates)

Note: Images for the tutorial were not updated, since we have to do a more extensive update anyways we'll do that in a separate PR.

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[x] Documentation content changes
[ ] Other... Please describe:

[glaucia86]

LGTM