gh-140189: Use macos-14 runner for iOS CI tests

[freakboy3742]

We're currently seeing a 2-4% failure rate in iOS tests.

This appears to be caused by a problem with the GitHub Actions macos-15 environment; this environment has been having performance issues since August (see actions/runner-images#12777).

This PR reverts to the macos-14 runner, which apparently isn't subject to the issues the macos-15 runner is experiencing. This means we'll be running iOS tests on an older iOS release (Xcode 15.4, iOS 17.5); but since we're compiling with iOS 13 compatibility, this shouldn't impact anything.

• Issue: iOS CI and binary releases #140189

[freakboy3742]

@hugovk I've run the iOS tests 6 times today, and it's passed every time; that's not proof that the "missing simulator" problem is fixed, but it's about as good as we're going to get.

As a bonus, it seems to be significantly faster than the macos-15 runner as well (consistently <21 mins, from the look of it).

[hugovk]

And revert #142365, or give this a few days to check reliability?

[mhsmith]

I'd say give it a few days, just in case.

[miss-islington-app]

Thanks @freakboy3742 for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-142494 is a backport of this pull request to the 3.14 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 FreeBSD Refleaks 3.x (tier-3) has failed when building commit 9188483.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1613/builds/2486) and take a look at the build logs.
4. Check if the failure is related to this commit (9188483) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1613/builds/2486

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
    ~~~~~~~~~~^^
ResourceWarning: unclosed <socket.socket fd=8, family=2, type=1, proto=6, laddr=('127.0.0.1', 50293), raddr=('127.0.0.1', 50294)>
Task was destroyed but it is pending!
task: <Task pending name='Task-1973' coro=<BaseSelectorEventLoop._accept_connection2() done, defined at /buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py:217> wait_for=<Future pending cb=[Task.task_wakeup()]>>
Warning -- Unraisable exception
Exception ignored while calling deallocator <function _SelectorTransport.__del__ at 0x83ee27050>:
Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py", line 873, in __del__
    _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
    ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ResourceWarning: unclosed transport <_SelectorSocketTransport closing fd=8>
k


Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
    ~~~~~~~~~~^^
ResourceWarning: unclosed <socket.socket fd=9, family=2, type=1, proto=6, laddr=('127.0.0.1', 52507), raddr=('127.0.0.1', 52508)>
Task was destroyed but it is pending!
task: <Task pending name='Task-1740' coro=<BaseSelectorEventLoop._accept_connection2() done, defined at /buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py:217> wait_for=<Future finished exception=ConnectionResetError()>>
Future exception was never retrieved
future: <Future finished exception=ConnectionResetError()>
Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/asyncio/sslproto.py", line 581, in _on_handshake_complete
    raise handshake_exc
ConnectionResetError
Warning -- Unraisable exception
Exception ignored while calling deallocator <function _SelectorTransport.__del__ at 0x845339b50>:
Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py", line 873, in __del__
    _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
    ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ResourceWarning: unclosed transport <_SelectorSocketTransport closing fd=9>
k