Ruby is continuing its path of requiring more gems to be specified. win32ole is next on the list (among others) and will start warning in Ruby 3.4: ruby/ruby@f365bef

Usage is here, to get the number of cores on windows:

Something like the following may be a suitable replacement:

IO.popen("wmic cpu get NumberOfCores", &:read).scan(/\d+/).map(&:to_i).reduce(:+)

Output of that command:
NumberOfCores \n\n4 \n\n\n\n

I have also openend the same report on parallel at grosser/parallel#345 if you are interested. Both implementations for this are basically the same.