fixes function typo

app.py

@@ -1,9 +1,9 @@
 import gradio as gr
 from fastai.learner import load_learner
 from fastai.vision.core import PILImage
-from huggingface_hub import hb_hub_download
+from huggingface_hub import hf_hub_download
 
-learner = load_learner(hb_hub_download("pinkpekoe/lesson2-bear-classifier", "export.pkl"))
+learner = load_learner(hf_hub_download("pinkpekoe/lesson2-bear-classifier", "export.pkl"))
 
 
 learner = load_learner('export.pkl')