Update README.md to download the model at the right location

this downloads the model at the right location to be used as prescribed in the example.

README.md

@@ -30,7 +30,7 @@ cd mlx-examples
 
 # Download model
 export HF_HUB_ENABLE_HF_TRANSFER=1
-huggingface-cli download --local-dir-use-symlinks False --local-dir phi-2 mlx-community/phi-2
+huggingface-cli download --local-dir-use-symlinks False --local-dir llms/phi2 mlx-community/phi-2
 
 # Run example
 python llms/phi2/phi2.py --prompt "My name is"