Update VisualQnA example with Falcon VLM

[arun-gupta]

Update VisualQnA example that uses Falcon VLM.

This would require to include Falcon as part of the validation at https://github.com/opea-project/GenAIComps/tree/main/comps/llms. And then create an updated VisualQnA that would use this microservice to use Falcon VLM.