This was removed in 415f080c80 (Split wxGrid RANGE_SELECT event into
SELECTING and SELECTED, 2020-07-27) without preserving it for
compatibility. Do define it now, just as it was done for the non-CMD
equivalent of this macro EVT_GRID_RANGE_SELECT.
Also update the documentation to fix a typo from e2f316b19d (Mention
that wxEVT_GRID_RANGE_SELECT{ED,ING} are new in 3.1.5, 2020-08-18).