Fix GNN model loading to specify CPU mapping for compatibility

src/demo.py

@@ -40,7 +40,7 @@ if "setup_complete" not in st.session_state:
                 dropout_rate=0.5,
             )
             undirected_gnn_model.load_state_dict(
-                torch.load(config.GNN_MODEL_PATH)
+                torch.load(config.GNN_MODEL_PATH, map_location=torch.device("cpu"))
             )
             st.session_state.undirected_gnn_model = undirected_gnn_model
             st.session_state.undirected_graph_data = undirected_graph_data