[pradoepargne] Make module completely inherit from Humanis

The Prado website has been engulfed by Humanis.
It is currently 100% broken but works when using the Humanis URLs.
Since pradoepargne now behaves exactly like humanis, there is no point
in keeping a browser.py and a pages.py since it works with total
inheritance from humanis.

Closes: 35971@sibi, 35867@sibi, 36065@sibi