games/anki: Switch to PyQt6

• This also fixes runtime errors [1] that occur in environments where PyQt5 and PyQt6 are present. In that case Anki prefers PyQt6 over PyQt5 upon invocation which leads then to following error:

$ anki
Running with temporary Qt5 compatibility shims.
Run with DISABLE_QT5_COMPAT=1 to confirm compatibility with Qt6.
Traceback (most recent call last):

File "/usr/local/bin/anki", line 7, in <module>
  import aqt
File "/usr/local/share/anki/aqt/__init__.py", line 74, in <module>
  from aqt.main import AnkiQt  # isort:skip
File "/usr/local/share/anki/aqt/main.py", line 20, in <module>
  import aqt.forms
File "/usr/local/share/anki/aqt/forms/__init__.py", line 1, in <module>
  from . import about
File "/usr/local/share/anki/aqt/forms/about.py", line 3, in <module>
  from .about_qt6 import *
File "/usr/local/share/anki/aqt/forms/about_qt6.py", line 45, in <module>
  import icons_rc

ModuleNotFoundError: No module named 'icons_rc'

• Amend a minor issue while I'm here: devel/py-sip is only required for build, set it accordingly.

• Bump PORTREVISION due changed dependencies and to regenerate the code (rust, js) in conjunction with PyQt6.

Reported by: Robin Dapp, Michael Reim (via e-mail) [1]
MFH: No (PyQt6 not present in 2023Q1)