MDL-81634 core: Fix implicitly defined nullables in lib/google

The version of this library we use is well and truly deprecated. These
will not be fixed upstream so we must do so.

lib/google/readme_moodle.txt

@@ -55,6 +55,8 @@ Local changes (to reapply until upstream upgrades contain them):
       ```
     * MDL-46563 - PHP 8.3 compliance
       - Converted use of `get_class()` to `static::class`
+    * MDL-81634 - PHP 8.4 compliance
+      - Implicitly defined nullables
 
 Information
 -----------

lib/google/src/Google/Http/REST.php

@@ -71,7 +71,7 @@ class Google_Http_REST
    * @param Google_Client $client
    * @return mixed|null
    */
-  public static function decodeHttpResponse($response, Google_Client $client = null)
+  public static function decodeHttpResponse($response, ?Google_Client $client = null)
   {
     $code = $response->getResponseHttpCode();
     $body = $response->getResponseBody();

lib/google/src/Google/IO/Exception.php

@@ -38,8 +38,8 @@ class Google_IO_Exception extends Google_Exception implements Google_Task_Retrya
   public function __construct(
       $message,
       $code = 0,
-      Exception $previous = null,
-      array $retryMap = null
+      ?Exception $previous = null,
+      ?array $retryMap = null
   ) {
     if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
       parent::__construct($message, $code, $previous);

lib/google/src/Google/Service/Exception.php

@@ -46,9 +46,9 @@ class Google_Service_Exception extends Google_Exception implements Google_Task_R
   public function __construct(
       $message,
       $code = 0,
-      Exception $previous = null,
+      ?Exception $previous = null,
       $errors = array(),
-      array $retryMap = null
+      ?array $retryMap = null
   ) {
     if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
       parent::__construct($message, $code, $previous);