Fix WFH data input columns in trip_generation_model.py

[kcazzatoCMAP]

In trip_generation_model.py
ln 306 - specifies columns labels for wfhFile (HH_WFH_STATUS.CSV)
ln 307 - specifies columns to drop from wfhFile

WFH procedures were updated and no longer includes 4 columns (tc14_not_working was removed) but remained in the code
Need to update the logic to remove 'tc14_not_working' as a column in these two lines