fix docstring (#383)

![Screenshot 2022-12-19 at 11 06 48
AM](https://user-images.githubusercontent.com/43734688/208468970-5cb9bafb-f535-486e-b41f-312a2f9ffffb.png)

langchain/llms/huggingface_pipeline.py

@@ -26,7 +26,7 @@ class HuggingFacePipeline(LLM, BaseModel):
                 model_id="gpt2", task="text-generation"
             )
     Example passing pipeline in directly:
-    .. code-block:: python
+        .. code-block:: python
 
             from langchain.llms.huggingface_pipeline import HuggingFacePipeline
             from transformers import AutoModelForCausalLM, AutoTokenizer, pipeline