Fixes the following error with pyqt6:
File "/home/pierre/dev/bitcoin-abc/electrum/electrumabc_gui/qt/transaction_dialog.py", line 225, in __init__
b.setShortcut(QKeySequence(Qt.ALT + Qt.Key_Q))
~~~~~~~^~~~~~~~~~
TypeError: unsupported operand type(s) for +: 'Modifier' and 'Key'