Update the default chat model id for the Gemini chat model

[fjuma]

The default chat model id for the Gemini chat model is gemini-1.5-flash. This model was discontinued on Sept. 24th.

Attempting to use this model results in the following error:

org.jboss.resteasy.reactive.ClientWebApplicationException: Received: 'Not Found, status code 404' when invoking REST Client method: 'io.quarkiverse.langchain4j.ai.runtime.gemini.AiGeminiRestApi#generateContent'

The default chat model id should be updated to use Gemini 2.0 Flash or newer.

[geoand]

Thanks for reporting!

Would you like to contribute the fix?

[fjuma]

@geoand Yes, I can work on the fix.

[geoand]

🙏🏽