remove Assign from parallel black list

mindspore/ccsrc/frontend/parallel/node_check.cc

@@ -74,7 +74,6 @@ const std::set<std::string> BLACK_LIST = {TUPLE_GETITEM,
                                           DROPOUT_GEN_MASK,
                                           EMBED,
                                           CREATINSTANCE,
-                                          ASSIGN,
                                           REF_TO_EMBED,
                                           STOP_GRADIENT};