tests: kernel/sleep: exclude npcx platforms from the test

According the specification, in extreme cases, the deviation of the APB
clock and LFCLK clock can reach up to +/-1% (+/- 10ms).
Therefore, exclude npcx platforms from the test because it required 1ms
accuracy.

fixes: #66185

Signed-off-by: Jun Lin <CHLin56@nuvoton.com>