Hooks: add_filter() used for login_head action

[apermo]

Problem

In wp-includes/default-filters.php at line 388, add_filter() is used to register a callback on the login_head hook, but this hook is fired with do_action() — making it an action, not a filter.

add_filter( 'login_head', 'wp_resource_hints', 8 );

Notably, line 387 correctly uses add_action() for the same hook:

add_action( 'login_head', 'wp_robots', 1 );
add_filter( 'login_head', 'wp_resource_hints', 8 );

Where the hook fires

• src/wp-login.php:127 — do_action( 'login_head' )

Fix

Change add_filter() to add_action().

Related to https://core.trac.wordpress.org/ticket/64224