These code snippets can be used in your theme’s function.php file or added to your site using a plugin like code snippets.
Disable Auto Update Plugin and Theme Emails:
This code snippet will prevent WordPress from sending emails notifying you of theme or plugin auto updates.
<?php
//Disable plugin auto-update email notification
add_filter('auto_plugin_update_send_email', '__return_false');
//Disable theme auto-update email notification
add_filter('auto_theme_update_send_email', '__return_false');
https://smartwp.com/disable-wordpress-auto-update-email-notifications/