[libc++] Change `std::numeric_limits` to just `numeric_limits` in <chrono>.

The namespace is unnecessary, and libc++ style is not to include it on type names.
(As opposed to function names, where qualification affects ADL; and in certain
function signatures where `std::` and `_VSTD::` might be mangled differently.
This is none of those situations.)

GitOrigin-RevId: 5f58374bbef356a4fd1565426257a4a24478a880
1 file changed