WordPress at a glance
function is not described

do_undismiss_core_update() WP 2.7.0

No Hooks.

Return

Nothing (null).

Usage

do_undismiss_core_update();

Code of do undismiss core update: wp-admin/update-core.php WP 5.2.2

<?php
function do_undismiss_core_update() {
	$version = isset( $_POST['version'] ) ? $_POST['version'] : false;
	$locale  = isset( $_POST['locale'] ) ? $_POST['locale'] : 'en_US';
	$update  = find_core_update( $version, $locale );
	if ( ! $update ) {
		return;
	}
	undismiss_core_update( $version, $locale );
	wp_redirect( wp_nonce_url( 'update-core.php?action=upgrade-core', 'upgrade-core' ) );
	exit;
}