tests/test_cache.py and Python >= 3.12: SyntaxWarning: invalid escape sequence '\w'

[wiene]

tests/test_cache.py yields the following syntax warning starting with Python 3.12 (tested using Lark 1.2.1):

/path/to/lark/tests/test_cache.py:150: SyntaxWarning: invalid escape sequence '\w'

See https://github.com/lark-parser/lark/actions/runs/10367391039/job/28698690278 for an example.