Remove param 'N.eff'; its value should always be length(skill_A)

Hi @cdelgado

This is the improvement for your comment For !128 (comment 196754). I simply removed the parameter N.eff and in the function, I kept the part for N.eff = NA, which means N.eff = length(skill_A). Let me know if there is any problem, thanks!

Best,
An-Chi