After convertion of the ImageCrop widget to an Owl component [1], the call to `this.displayNotification` no longer applies. In fact, it produces a traceback when trying to crop an image that cannot be cropped (base64-encoded image not yet converted to an attachment, for example). This commit replaces such call for the more suitable notification service's `add` method. task-3471481 [1]: https://github.com/odoo/odoo/commit/d7245d2abf528d093226c80e40975e63d61e8997 closes odoo/odoo#132726 Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>