App Passwords: Include authorization rewrite rule in default multisite .htaccess

This rule was previously added to `WP_Rewrite`, but multisite uses a different .htaccess generation mechanism.

Props pbiron.
Fixes #51772.
See [49109].


git-svn-id: https://develop.svn.wordpress.org/trunk@49607 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/network.php

@@ -640,6 +640,7 @@ define('BLOG_ID_CURRENT_SITE', 1);
 
 		$htaccess_file = <<<EOF
 RewriteEngine On
+RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
 RewriteBase {$base}
 RewriteRule ^index\.php$ - [L]
 {$ms_files_rewriting}