Background
Getting annoyed by “…Some plugins have automatically updated to their latest versions on your site at…”?
Solution
Add this to your child theme’s functions.php:
<?php
// Disable auto-update email notifications for plugins.
add_filter( 'auto_plugin_update_send_email', '__return_false' );
// Disable auto-update email notifications for themes.
add_filter( 'auto_theme_update_send_email', '__return_false' );