Update ChatQnA example with Falcon LLM

[arun-gupta]

Update ChatQnA example that uses Falcon as the LLM.

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 ChatQnA that would use this microservice to use Falcon LLM.