[18.0][FIX] web_favicon: use sanitized cids cookie

[remi-filament]

company ids separated by - is only available on sanitized request as per : https://github.com/odoo/odoo/blob/fcc5a90d2d5754923676b11031e37f52729402fd/addons/web/models/ir_http.py#L46

when using request.httprequest.cookies.get("cids"), you get a comma separated list instead and therefore the lines after the ones assigning company_id are failing when you get more than 2 companies active (because trying to cast to integer a string with potential multiple commas)