[IMP] WMS : Made o2m field 'valuation_adjustment_lines' as readonly in l...

Purpose : 
In WMS > Landed Costs : No need of " Add an item " in Valuation Adjustments, because all values of valuation adjustments generate automatically from pickings.
So, valuation_adjustment_line field should be readonly.

Task : https://www.odoo.com/web#id=9363&view_type=form&model=project.task&menu_id=3942&action=327