class WP_User(), mark prop $deleted as deprecated

[ignatiusjeroe]

I've search the source code for the utility of column deleted in database table Users. There is only one mention of it in function wp_update_user_counts(), but that seems like irrelevant since 'spam' seems like its replacement. If that is the case the WP_User class should change the comment

current:

* @property string $deleted

replacement:

* @property string $deleted Deprecated. Use {@see $spam} instead.

mark

### Ticket: https://core.trac.wordpress.org/ticket/61149

## Description
Ensure consistent handling of 'checked' property in wp_update_plugins() function.

• This PR addresses ticket #61149 by marking the $deleted property in the WP_User class as deprecated.
• After reviewing the WordPress core code, it was found that the $deleted column is only mentioned once in the function wp_update_user_counts().
• This reference appears to be irrelevant since the $spam property has replaced its functionality. To reflect this change, the documentation for the WP_User class is updated accordingly.

## Changes Made

• Updated the docblock for the $deleted property in the WP_User class to mark it as deprecated.
• Added a reference to use the $spam property instead.