Update readme to fix typo in model ID

There's a small typo in the readme example which prevents the copied example from running right away - "epinnock/wizardcoder-1b-merged" vs. "epinnock/wizardcoder1b-merged".

README.md

@@ -37,7 +37,7 @@ Based on Previous works of @WizardLM
 # pip install -q transformers
 from transformers import AutoModelForCausalLM, AutoTokenizer
 
-checkpoint = "epinnock/wizardcoder1b-merged"
+checkpoint = "epinnock/wizardcoder-1b-merged"
 device = "cuda" # for GPU usage or "cpu" for CPU usage
 
 tokenizer = AutoTokenizer.from_pretrained(checkpoint)