How can I remove the editor from the ‘main posts page’?

Question

WordPress already does this by default, so long as that page doesn’t have any existing content. Plus it adds a notice explaining why the editor isn’t there.

These are the lines already in WordPress Core:

if ( $post_ID == get_option( 'page_for_posts' ) && empty( $post->post_content ) ) {
    add_action( 'edit_form_after_title', '_wp_posts_page_notice' );
    remove_post_type_support( $post_type, 'editor' );
}

Lines 74-76 here: https://github.com/WordPress/WordPress/blob/master/wp-admin/edit-form-advanced.php