remove hardcoded /wp-admin

Author: masteradhoc

src/wp-includes/functions.php

@@ -1718,10 +1718,8 @@ function do_robots() {
 	$output = "User-agent: *\n";
 	$public = (bool) get_option( 'blog_public' );
 
-	$site_url = parse_url( site_url() );
-	$path     = ( ! empty( $site_url['path'] ) ) ? $site_url['path'] : '';
-	$output  .= "Disallow: $path/wp-admin/\n";
-	$output  .= "Allow: $path/wp-admin/admin-ajax.php\n";
+	$output .= 'Disallow: ' . (string) wp_parse_url( admin_url(), PHP_URL_PATH ) . "\n";
+	$output .= 'Allow: ' . (string) wp_parse_url( admin_url( 'admin-ajax.php' ), PHP_URL_PATH ) . "\n";
 
 	/**
 	 * Filters the robots.txt output.