PCA CV step uses all processes regardless of the parameter settings

[cflerin]

In the config file, setting the nCores parameter has no effect on how many processes are used. It always uses all processes available.

pcacv {
   container = 'vibsinglecellnf/pcacv:0.1.0'
   find_optimal_npcs {
      accessor = '@assays$RNA@scale.data'
      nCores = 20
   }
}

The R script has a default value of 1 process, but this doesn't seem to be used either.