Update for qt6

[RisingOrange]

I just replaced an import from PyQt5 with one from aqt.qt to make it more future proof (and cleaned up other imports). The add-on works in Anki 2.1.50 with qt6.

[DoctorToBeIn23]

I am getting an error on qt6 as well when V3 scheduler is on

Error
An error occurred. Please start Anki while holding down the shift key, which will temporarily disable the add-ons you have installed.
If the issue only occurs when add-ons are enabled, please use the Tools > Add-ons menu item to disable some add-ons and restart Anki, repeating until you discover the add-on that is causing the problem.
When you've discovered the add-on that is causing the problem, please report the issue to the add-on author.
Debug info:
Anki 2.1.55 (e3c3405f) Python 3.9.7 Qt 6.4.0 PyQt 6.4.0
Platform: macOS-11.5.2-arm64-arm-64bit
Flags: frz=True ao=True sv=3
Add-ons, last update check: 2022-12-03 20:15:44
Add-ons possibly involved: ⁨Straight Reward⁩

Caught exception:
Traceback (most recent call last):
File "aqt.webview", line 556, in handler
File "aqt.reviewer", line 532, in _onAnswerButton
File "aqt.reviewer", line 431, in _answerCard
File "aqt.hooks_gen", line 3807, in call
File "/Users/Jacob/Library/Application Support/Anki2/addons21/957961234/src/lib/review_hook.py", line 101, in
lambda ease_tuple, reviewer, card: on_will_answer_card(
File "/Users/Jacob/Library/Application Support/Anki2/addons21/957961234/src/lib/review_hook.py", line 85, in on_will_answer_card
check_straight_reward(gains, reviewer, card, ease_tuple[1])
File "/Users/Jacob/Library/Application Support/Anki2/addons21/957961234/src/lib/review_hook.py", line 64, in check_straight_reward
next_states = reviewer.get_next_states()
AttributeError: 'Reviewer' object has no attribute 'get_next_states'