[FIX] website: properly enable a website view from its generic view

Before this commit, when enabling a generic view from a specific website
context and that view already had a specific view for this website, the
view was duplicated again instead of writing on the already existing
specific one.

This is because we did not consider inactive views when checking if a
view that is being written already has a website-specific view.

closes odoo/odoo#28743