[CI] Use Python 3.12 for third-party stubtest

[srittau]

No description provided.

[srittau]

• atheris doesn't compile (last release 2023-08)
• boto fails to import boto.vendored.six (last release 2018-07!) (Remove boto #12848)
• openpyxl needs a stubtest allowlist update
• playsound doesn't compile (last release 2021-07)
• requests needs a stubtest allowlist update
• gdb fails with the following traceback???

Traceback (most recent call last):
  File "/tmp/stubtest-j8_r64qv/gdb_stubtest.py", line 22, in <module>
    from mypy.stubtest import main
  File "/tmp/stubtest-j8_r64qv/lib/python3.12/site-packages/mypy/stubtest.py", line 30, in <module>
    from pathlib import Path
  File "/usr/lib/python3.12/pathlib.py", line 19, in <module>
    from urllib.parse import quote_from_bytes as urlquote_from_bytes
  File "/usr/lib/python3.12/urllib/parse.py", line 36, in <module>
    import math
ModuleNotFoundError: No module named 'math'

[srittau]

I'm honestly stumped why gdb fails. Locally (also using Ubuntu 2024.04), this works.

[AlexWaygood]

There's also a couple of stubtest failures on wtforms still