[FIX] subscription: use an `@api.model` method for cron
[FIX] subscription: use an `@api.model` method for cron

Since the cron engine has been migrated to use the new-api (4ddc32313996c8cf6e8e6dffd2253aad8a144ccf),
cron methods should be defined as `@api.model`

dfang/odoo,hip-odoo/odoo,dfang/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,dfang/odoo,dfang/odoo,ygol/odoo,hip-odoo/odoo,dfang/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,ygol/odoo