Templates: Spruce up ADSL

[bms63]

Background Information

ADSL template needs a little love

The comment needs to be updated for input datasets -

and these source objects should be removed as the derive_vars_extreme_event() function replaced this method

Definition of Done

Comment updated and legacy code removed.

Great issue for @pharmaverse/admiral_comm and wanting to keep your admiral skills fresh :)

[jimrothstein]

I can take a look