Fix the version gate on the free-threaded profiler warning (#194697)

> IS_PYTHON_3_14_PLUS is always defined (as `PY_VERSION_HEX >= 0x030E0000`), so `!defined(IS_PYTHON_3_14_PLUS)` was always false and the warning never fired on 3.13t. Introduced in #178551, which almost certainly meant to check the macro's boolean value, not whether it's defined. Fix uses the macro's value instead.
>
> Test plan: compiled a probe with the guard against free-threaded 3.14 headers; old form is unreachable on every version, new form is reachable only when pinned to a 3.13 `PY_VERSION_HEX`.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/194697
Approved by: https://github.com/ryanzhang22