fix n_tpc_pmts option
Created by: jorana
Double check that the number of PMTs in the nT-configuration match up with the to_pe file (which is currently not there).
Also the reference previously pointing to straxen.n_tpc_pmts
was returning 248. Hence, I propose to rename this variable to avoid confusion.
@JelleAalbers would you say it makes sense to make a mock nt_to_pe
in the aux. files and parse the reference thereto here:
https://github.com/XENONnT/straxen/blob/master/straxen/contexts.py#L32