Renaming environ variable

Cloning this repo suggests that the environment variable should be TOKEN, not HF_TOKEN.
This also matches the token name on the frontend.

src/envs.py

@@ -4,7 +4,7 @@ from huggingface_hub import HfApi
 
 # Info to change for your repository
 # ----------------------------------
-TOKEN = os.environ.get("HF_TOKEN") # A read/write token for your org
+TOKEN = os.environ.get("TOKEN") # A read/write token for your org
 
 OWNER = "demo-leaderboard-backend" # Change to your org - don't forget to create a results and request dataset