Before this commit, any field requested to `_binary_record_content()`
when the model was `ir.attachment` would be considered as `raw`.
This assumption works at the moment but could lead to unexpected
behavior down the line.
see https://github.com/odoo/odoo/pull/86005#discussion_r824420219closesodoo/odoo#86524
X-original-commit: eeb93287f9a9027d0ce22f9fd3305a7ab081d69f
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>