FinisherRoutines stat isn't updated

[vbanos]

Methods FinisherRoutinesIncr and FinisherRoutinesDecr are not used.

globalStats.FinisherRoutinesFinisherRoutines is only used to display

"Finisher routines":       globalStats.FinisherRoutines.get(),

We should add FinisherRoutinesIncr and FinisherRoutinesDecr in https://github.com/internetarchive/Zeno/blob/main/internal/pkg/finisher/finisher.go#L80
but I'm not sure where because of the channels. Maybe here:
https://github.com/internetarchive/Zeno/blob/main/internal/pkg/finisher/finisher.go#L100