Convert docs for `wp_nav_menu()` arguments to a hash notation.

Fixes #27163.


git-svn-id: https://develop.svn.wordpress.org/trunk@27222 602fd350-edb4-49c9-b593-d223f7449a82
Fix reversed return logic in the `wp_nav_menu()` phpdoc.

See #27163.


git-svn-id: https://develop.svn.wordpress.org/trunk@27223 602fd350-edb4-49c9-b593-d223f7449a82