I18N: Replace hardcoded file name in translatable strings in...

I18N: Replace hardcoded file name in translatable strings in `wp-admin/setup-config.php` with a placeholder.

Props ramiy, danieltj.
Fixes #42161.
Built from https://develop.svn.wordpress.org/trunk@41904


git-svn-id: https://core.svn.wordpress.org/trunk@41738 1a063a9b-81f0-0310-95a4-ce76da25c4cd