Fix conditional check "Theme File Editor" menu

[Mamaduka]

Description

Follow-up for #37592.

It looks like I messed up something when doing initial tests and was getting incorrect results 🙇‍♂️

The _add_plugin_file_editor_to_tools isn't available when we're performing the check, so we still end up with two "Theme File Editor" sub-menu items.

Cord now uses wp_list_users for version check. We're using this function for similar checks in a few other places, so it should be safe.

Props to @costdev for discovering the issue 🥇

How has this been tested?

1. Running WP 5.9 beta 4
2. Go to the Dashboard and click on the "Tools" menu
3. It should only display a single "Theme File Editor" sub-menu item.

Types of changes

Bugfix

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[Mamaduka]

@aristath, do you mind approving this one as well? 🙇

P.S. Sorry about all the notifications.

[aristath]

Good catch! We missed this in the previous PR, I'm glad it was detected immediately 👍