kraken.spot.trade.create_order: stp_type should be stptype (#373)

Co-authored-by: Benjamin T. Schwertfeger <[email protected]>

Author: HFFP

src/kraken/spot/trade.py

@@ -328,7 +328,7 @@ def create_order(  # pylint: disable=too-many-branches,too-many-arguments # noqa
                 if not truncate
                 else self.truncate(amount=volume, amount_type="volume", pair=pair)
             ),
-            "stp_type": stptype,
+            "stptype": stptype,
             "starttm": starttm,
             "validate": validate,
             "reduce_only": reduce_only,