[REF] web_editor: remove relics of filter feature
[REF] web_editor: remove relics of filter feature

Previously, the media-dialog had a "filter" feature, where when changing
a background image for example, all backgrounds would show first in the
media-dialog. However, because this required to load all public
attachments in the database it was causing issues and was removed. The
backend code for this feature however was unfortunately forgotten, this
commit removes that code.

Part of https://github.com/odoo/odoo/pull/51517
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo