Update app.py

Fixed typo in the summarizer tool.

app.py

@@ -45,8 +45,8 @@ def summarize_text_tool(text:str)-> str:
         text: the text to be summaried
     """
     try:
-        hf_key = os.getEnv('hf_key')
-        client = InferenceClient(api_key=hf_key)
+        hf_token = os.getenv('hf_token')
+        client = InferenceClient(api_key=hf_token)
         messages = [
         	{
         		"role": "user",