`__extraAssetsForIframe` had been kept in `mass_mailing` and `web_editor` for historical reasons but was not used anymore. This removes it. X-original-commit: 88b91df3ff75bb0be9a84761cb251d0b7b3c976d Part-of: odoo/odoo#84513
`__extraAssetsForIframe` had been kept in `mass_mailing` and `web_editor` for historical reasons but was not used anymore. This removes it. X-original-commit: 88b91df3ff75bb0be9a84761cb251d0b7b3c976d Part-of: odoo/odoo#84513