Bump PyPy runtime to v3.9 @ GHA

[x612skm]

As we were encountering this -

 __________________ ERROR collecting testing/_py/test_local.py __________________
/opt/hostedtoolcache/PyPy/3.8.16/x64/lib/pypy3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
<frozen importlib._bootstrap>:1023: in _gcd_import
    ???
<frozen importlib._bootstrap>:1000: in _find_and_load
    ???
<frozen importlib._bootstrap>:984: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:680: in _load_unlocked
    ???
.tox/pypy3-xdist/lib/pypy3.8/site-packages/_pytest/assertion/rewrite.py:166: in exec_module
    source_stat, co = _rewrite_test(fn, self.config)
.tox/pypy3-xdist/lib/pypy3.8/site-packages/_pytest/assertion/rewrite.py:350: in _rewrite_test
    co = compile(tree, strfn, "exec", dont_inherit=True)
E   TypeError: expected some sort of stmt, but got <_ast.Store object at 0x0000000002142880>

Due to the PyPy version 3.8 which has a bug at its garbage collector and its EoL. Hence bumping the PyPy version to resolve the issue.

Closes #11771

[webknjaz]

Note for other maintainers: please, ignore this PR for now. I'm walking a mentee through the contribution process.

[webknjaz]

Looking at https://github.com/pytest-dev/pytest/actions/runs/9748380501/job/26903269973?pr=12557#step:6:138, it seems like this PR might also need to adjust the tests.

[patchback]

Backport to 8.2.x: 💚 backport PR created

✅ Backport PR branch: patchback/backports/8.2.x/a7d5a8eba9addd119432fa71880b51052a89812f/pr-12557

Backported as #12632

🤖 @patchback
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[nicoddemus]

@webknjaz just a quick reminder, probably would have been best to squash/merge this instead of a normal merge, as the individual commits do not add much to the history. 👍

[webknjaz]

@nicoddemus my understanding is that it's okay to use natural merge when the incoming commits aren't a mess. I usually only use the fake merge modes like squash when nothing else can save the history.

[nicoddemus]

I'm not sure this is a consensus, but I usually only keep commits when they make sense separately, which was not the case here: I don't see the value of having a commit implementing a feature, a separate commit adding a changelog, and another one adding someone to AUTHORS -- this is of course fine for development, but it is not useful months or years down the road when reviewing the history.

@RonnyPfannschmidt @bluetech @The-Compiler what are your opinions here?

[nicoddemus]

Actually I will move this to a separate discussion, I think it is probably best to discuss this properly.

[nicoddemus]

#12633 👍