Update app.py

app.py

@@ -62,7 +62,7 @@ def configure_skidl_libs():
     logger.info("Set dummy KiCad environment variables to suppress warnings")
 
 def cleanup_old_files():
-    """Clean up temporary files older than  salted
+    """Clean up temporary files older than 1 hour."""
     temp_dir = tempfile.gettempdir()
     for f in os.listdir(temp_dir):
         if f.endswith('.net') and os.path.getmtime(os.path.join(temp_dir, f)) < time.time() - 3600: