Necessary to get coverage of the new event functions.
Deletes the case that called usleep(delay) for mp_hal_delay_ms(), it seems
like this wouldn't have ever happened anyhow (MICROPY_EVENT_POOL_HOOK is
always defined for the unix port).
This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>