revert change to generate readme command

recipes/README.md

@@ -65,5 +65,5 @@ tune --nnodes 1 --nproc_per_node 2 finetune_lora --config alpaca_llama2_lora_fin
 
 To run the generation recipe, run this command from inside the main `/torchtune` directory:
 ```
-python -m recipes.alpaca_generate --native-checkpoint-path /tmp/finetune-llm/model_0.ckpt --tokenizer-path ~/llama/tokenizer.model --instruction "What is some cool music from the 1920s?"
+python -m recipes.alpaca_generate --native-checkpoint-path /tmp/finetune-llm/model_0.ckpt --tokenizer-path ~/llama/tokenizer.model --input "What is some cool music from the 1920s?"
 ```