Fix Google Schema error for custom logos on WordPress sites.

functions.php

<?php
/**
 * Fix Google Schema error, "The property logo is not recognised by Google for an object of type WPHeader".
 *
 * @param   string  $html  The logo HTML.
 *
 * @return  string  The modified HTML.
 */
add_filter( 'get_custom_logo', function( $html ) {
    $html = str_replace( 'itemprop="logo"', 'itemprop="image"', $html );
    return $html;
});