fix documentation

Signed-off-by: Etienne LESOT <etienne.lesot@rte-france.com>

pypowsybl/network/impl/network.py

@@ -1131,6 +1131,7 @@ def get_dangling_lines(self, all_attributes: bool = False, attributes: List[str]
               - **connected**: ``True`` if the dangling line is connected to a bus
               - **fictitious** (optional): ``True`` if the dangling line is part of the model and not of the actual network
               - **pairing_key**: the pairing key associated to the dangling line, to be used for creating tie lines.
+              - **ucte-xnode-code**: deprecated for pairing key.
               - **tie_line_id**: the ID of the tie line if the dangling line is paired
 
             This dataframe is indexed by the id of the dangling lines