Update README.md: Update Model Description to reference Falcon-40B as the base model for falcon-40b-instruct

The current readme.md is pointing to falcon-7b as the base model for falcon-40b-instruct.
This PR points to falcon-40b as the base model for falcon-40b-instruct.

README.md

@@ -64,7 +64,7 @@ for seq in sequences:
 - **Model type:** Causal decoder-only;
 - **Language(s) (NLP):** English and French;
 - **License:** Apache 2.0;
-- **Finetuned from model:** [Falcon-7B](https://huggingface.co/tiiuae/falcon-7b).
+- **Finetuned from model:** [Falcon-40B](https://huggingface.co/tiiuae/falcon-40b).
 
 ### Model Source