Don't run update checks for AJAX requests after [31168].

fixes #30947.
Built from https://develop.svn.wordpress.org/trunk@31701


git-svn-id: http://core.svn.wordpress.org/trunk@31682 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/update.php

@@ -663,7 +663,3 @@ function wp_clean_update_cache() {
 	wp_clean_themes_cache();
 	delete_site_transient( 'update_core' );
 }
-
-if ( ( ! is_main_site() && ! is_network_admin() ) || ( defined( 'DOING_AJAX' ) && DOING_AJAX ) ) {
-	return;
-}