k_sleep parameter in the latest Zephyr API

[dinayuil]

Hi, When I try to build the code in the thread start exercise, the k_sleep gave error. I found that the parameter k_sleep takes should be in type k_timeout_t (https://docs.zephyrproject.org/apidoc/latest/group__thread__apis.html#ga48d4b041790454da4d68ac8711f29657). And the code can be changed to k_sleep(K_MSEC(500)), or change the define of SLEEPTIME.

https://github.com/maksimdrachov/zephyr-rtos-tutorial/blob/36b3f5b5a1e1c611cba3cf2b6f78a3e7ae9de5d5/exercises/threads/thread-start/src/main.c#L19