Revert another instance where a `WP` property was assigned to a one-time variable for inline docs purposes.

Referencing a non-existent variable only in the docs here would have been the better choice.

See #25495.


git-svn-id: https://develop.svn.wordpress.org/trunk@25946 602fd350-edb4-49c9-b593-d223f7449a82