Increase STM32 default deep sleep latency to 4ms
Increase STM32 default deep sleep latency to 4ms

Recent measurements have shown that the total wake-up latency can be more
than the 3ms initially set. It was measured as 3,7ms on DISCO_L475VG_IOT01A
target and 3,1ms on NUCLEO_L073RZ target. So set it to 4ms to be on the
safe side.

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