Currently user cannot disable notifications for deleting attachments without disabling notifications for the Issue Updates events.

There should be a new separate event for adding an attachment and another event for deleting an attachment in order to enable specific notifications for these.

Workaround

Automation workaround to add a comment whenever an attachment is created
Please keep in mind your Automation service limits when using.

Webhooks setup. Note the query string ?issue=${issue.key} at the end of the URL:

Automation rule setup (You should change the comment to "Attachment deleted":