[Bugfix] Set enable_prefix_caching=True in prefix caching example (vl…

…lm-project#3703)

examples/offline_inference_with_prefix.py

@@ -22,7 +22,7 @@
 sampling_params = SamplingParams(temperature=0.0)
 
 # Create an LLM.
-llm = LLM(model="facebook/opt-125m")
+llm = LLM(model="facebook/opt-125m", enable_prefix_caching=True)
 
 generating_prompts = [prefix + prompt for prompt in prompts]