Update app.py

Fix `try` syntax

app.py

@@ -15,7 +15,7 @@ def search_web(query:str)-> str:
     Args:
         query: What to search for.
     """
-    try
+    try:
         results = search_tool.run(query)
         return f"Search results for '{query}':\n" + "\n".join(results)
     except Exception as e: