Add this line to your function file to disable default password change notification in wordpress.
To disable the notice of changed email sent by the wp_update_user() function, simply use the filter hook to return false:
add_filter( 'send_email_change_email', '__return_false' );
Reference - https://codex.wordpress.org/Plugin_API/Filter_Reference/send_email_change_email
Method 2
if ( !function_exists( 'wp_password_change_notification' ) ) {
function wp_password_change_notification() {}
}
put this code in your plugin file for method 2.
Note - it will not work if you put in your theme function file
Reference - http://www.wpbeginner.com/wp-tutorials/how-to-disable-lostchanged-password-emails-in-wordpress/
Method 3 - use this plugin to get required output
https://wordpress.org/plugins/manage-notification-emails/