Docs: Add missing inline doc descriptions in wp-admin/includes/misc.php

## Description

Add missing inline doc @param descriptions and function summary in src/wp-admin/includes/misc.php.

### Functions fixed:

• update_recently_edited() — missing @param $file description
• update_home_siteurl() — missing @param $old_value and @param $value descriptions
• show_message() — missing @param $message description
• saveDomDocument() — missing @param $doc and @param $filename descriptions
• wp_color_scheme_settings() — missing function summary description

## Changes

• No functional changes, documentation only.
• Follows the ​WordPress Inline Documentation Standards.

## Trac Ticket

Fixes https://core.trac.wordpress.org/ticket/64920