Fix author meta tag suppressed for CPTs with author support

[thisismyurl]

Description

Custom post types configured with 'author' in their supports array do not output the author meta tag, even when using the wpseo_meta_author filter — the filter is never reached for any object_sub_type that isn't the literal string 'post'.

Root cause: Meta_Author_Presenter::get() contains a guard that compares object_sub_type against the hardcoded string 'post' and bails out before the wpseo_meta_author filter can fire for any other post type.

Before:

if ( $this->presentation->model->object_sub_type !== 'post' ) {
    return '';
}

Fix: Replace the hardcoded equality check with post_type_supports():

if ( ! \post_type_supports( $this->presentation->model->object_sub_type, 'author' ) ) {
    return '';
}

The tag is now emitted for any post type that declares 'author' support — including built-in types that already had it and CPTs registered with that support. Types without the feature continue to receive no tag.

How to test

1. Register a CPT with 'supports' => [ 'title', 'editor', 'author' ]
2. Create a post of that type and view it on the frontend
3. Check page source — <meta name="author" content="..." /> should appear
4. Optionally add a wpseo_meta_author filter — confirm it fires and the return value is used

Changelog label

Could a maintainer please apply changelog: bugfix? As an external contributor I'm unable to add labels, and I understand pr-validation.yml requires one before merge.

Credits

props @thisismyurl (full disclosure: AI helped me identify the issue and verify my work)

Closes #23193