RAIL_TIME_RELATIVE in doc doesn't exist

[nbrunner]

in rail.h, RAIL_TIME_RELATIVE is used instead of RAIL_TIME_DELAY:

simplicity_sdk/platform/radio/rail_lib/common/rail.h

Line 1018 in da66128

/// RAIL_SetMultiTimer(&tmr1, 1000, RAIL_TIME_RELATIVE, &timerCb, NULL);

simplicity_sdk/platform/radio/rail_lib/common/rail.h

Line 982 in da66128

/// RAIL_SetTimer(railHandle, 1000, RAIL_TIME_RELATIVE, &timerCb);