py(deps[dev]) mypy 2.3.0 -> 2.3.1

why: A patch release with no CHANGELOG entry, so the diff is the record:
four commits, three of them mypyc runtime fixes (clearing a coroutine's
environment on completion, `default_factory` on inherited dataclasses,
and a crash on double-yielding Iterators) and one type-checker fix, a
crash when unpacking the return value of an overload. This project runs
mypy as a checker rather than compiling with mypyc, so the overload
crash is the fix that reaches it.

what:
- uv.lock: mypy 2.3.0 -> 2.3.1

See also:
- python/mypy@v2.3.0...v2.3.1
- https://pypi.org/project/mypy/2.3.1/

Author: tony