The email address associated with Softaculous notices is not the same email address as within the cPanel Control Panel or Billing/Support System.
To update this setting, it's actually inside of Softaculous itself. If you go into the cPanel and then into the Softaculous area, on the top right side of the page there's a MAIL ENVELOPE icon. Click this.
This will allow you to update the email address and set settings regarding Installation emails, Removal of Installations and also Modification Emails when something is modified. It does not have an option to disable Script Update alerts however. Generally, when a new version is released, you'd want to receive those alerts so that you can make the necessary updates with your software to avoid hacks and exploits.