Removal of ping from google site maps

See https://developers.google.com/search/blog/2023/06/sitemaps-lastmod-ping for context.

Accordingly removed all references to notification config and/or ping.

_config/googlesitemaps.yml

@@ -4,7 +4,6 @@ Name: googlesitemaps
 Wilr\GoogleSitemaps\GoogleSitemap:
   enabled: true
   objects_per_sitemap: 1000
-  google_notification_enabled: false
   use_show_in_search: true
 ---
 Only:

docs/en/index.md

@@ -38,14 +38,10 @@ After: googlesitemaps
 Wilr\GoogleSitemaps\GoogleSitemap:
   enabled: true
   objects_per_sitemap: 1000
-  google_notification_enabled: false
   use_show_in_search: true
 ```
 
-You can now alter any of those properties to set your needs. A popular option
-is to turn on automatic pinging so that Google is notified of any updates to
-your page. You can set this in the file we created in the last paragraph by
-editing the `google_notification_enabled` option to true
+You can now alter any of those properties to set your needs.
 
 ```yml
 ---
@@ -54,9 +50,8 @@ After: googlesitemaps
 ---
 Wilr\GoogleSitemaps\GoogleSitemap:
   enabled: true
-    objects_per_sitemap: 1000
-    google_notification_enabled: true
-    use_show_in_search: true
+  objects_per_sitemap: 1000
+  use_show_in_search: true
 ```
 
 ### Including DataObjects

src/Extensions/GoogleSitemapExtension.php

@@ -73,24 +73,6 @@ class GoogleSitemapExtension extends DataExtension
         return $can;
     }
 
-
-    /**
-     * @return void
-     */
-    public function onAfterPublish()
-    {
-        GoogleSitemap::ping();
-    }
-
-    /**
-     * @return void
-     */
-    public function onAfterUnpublish()
-    {
-        GoogleSitemap::ping();
-    }
-
-
     /**
      * The default value of the priority field depends on the depth of the page in
      * the site tree, so it must be calculated dynamically.

src/GoogleSitemap.php

@@ -29,17 +29,8 @@ use ReflectionException;
  * The GoogleSitemap handle requests to 'sitemap.xml' the other two classes are
  * used to render the sitemap.
  *
- * You can notify ("ping") Google about a changed sitemap automatically whenever
- * a new page is published or unpublished.
- *
- * By default, Google is not notified, and will pick up your new sitemap
- * whenever the GoogleBot visits your website.
- *
- * To Enable notification of Google after every publish set google_notification_enabled
- * to true in the googlesitemaps.yml config file.
- *
- * This file is usually located in the _config folder of your project folder.
- * e.g mysite/_config/googlesitemaps.yml
+ * The config file is usually located in the _config folder of your project folder.
+ * e.g. app/_config/googlesitemaps.yml
  *
  * <example>
  *  ---
@@ -49,7 +40,6 @@ use ReflectionException;
  *  Wilr\GoogleSitemaps\GoogleSitemap:
  *      enabled: true
  *      objects_per_sitemap: 1000
- *      google_notification_enabled: true
  *      use_show_in_search: true
  * </example>
  *
@@ -84,15 +74,6 @@ class GoogleSitemap
      */
     private static $exclude_redirector_pages = true;
 
-    /**
-     * @config
-     *
-     * @var array
-     */
-    private static $search_indexes = [
-        'google' => 'http://www.google.com/webmasters/sitemaps/ping?sitemap='
-    ];
-
     /**
      * Decorates the given DataObject with {@link GoogleSitemapDecorator}
      * and pushes the class name to the registered DataObjects.
@@ -452,41 +433,6 @@ class GoogleSitemap
         return static::inst()->getSitemaps();
     }
 
-    /**
-     * Notifies search indexes about changes to your sitemap. This behavior is disabled
-     * by default, to enable, read the documentation provided in the docs folder.
-     *
-     * After notifications have been enabled, every publish / unpublish of a page.
-     * will notify enabled search indexes of the update.
-     *
-     * If the site is in development mode no ping will be sent.
-     *
-     * @return boolean
-     */
-    public static function ping()
-    {
-        if (!self::enabled() || Director::isDev()) {
-            return false;
-        }
-
-        $location = urlencode(Controller::join_links(
-            Director::absoluteBaseURL(),
-            'sitemap.xml'
-        ));
-
-        $response = true;
-
-        foreach (self::config()->search_indexes as $name => $url) {
-            $configName = $name . '_notification_enabled';
-
-            if (self::config()->$configName) {
-                $response = $response && file_get_contents($url . $location);
-            }
-        }
-
-        return $response;
-    }
-
     /**
      * Is GoogleSitemap enabled?
      *