asyncio.iscoroutinefunction() deprecation warnings in Python 3.14

[paultiq]

In 3.14, async code using filelock now emits the following warning: DeprecationWarning: 'asyncio.iscoroutinefunction' is deprecated and slated for removal in Python 3.16; use inspect.iscoroutinefunction() instead

Reproduction

 python -c "import asyncio, filelock; asyncio.run(filelock.AsyncFileLock('x').acquire(timeout=1))"

....venv\Lib\site-packages\filelock\asyncio.py:268: DeprecationWarning: 'asyncio.iscoroutinefunction' is deprecated and slated for removal in Python 3.16; use inspect.iscoroutinefunction() instead

What needs to change

filelock/src/filelock/asyncio.py

Line 268 in 77d02f5

if asyncio.iscoroutinefunction(method):

Python deprecation notice

https://docs.python.org/3.14/whatsnew/3.14.html explains: "asyncio.iscoroutinefunction() is deprecated and will be removed in Python 3.16; use inspect.iscoroutinefunction() instead. (Contributed by Jiahao Li and Kumar Aditya in gh-122875.)"

[paultiq]

May I suggest adding 3.14t (free threading build) to the matrix, in addition to 3.14?

[gaborbernat]

PR welcome 😊