Register Google Maps API Key for ACF

define-google-maps-api-key-for-acf.php

<?php

// Define this in the site's wp-config.php file.
define('GOOGLE_API_KEY', 'your-google-api-key-here');

// Add this to your functions.php file, or a config plugin/MU plugin. 
add_filter( 'acf/fields/google_map/api', function ( $api ) {
	$api['key'] = GOOGLE_API_KEY;

	return $api;
} );