Docs: Document the $wp_version global in update_core().

Follow-up to [17576], [22226], [31124], [32643], [39687].

Props upadalavipul, mukesh27, johnbillion, SergeyBiryukov.
Fixes #63496.
Built from https://develop.svn.wordpress.org/trunk@60265


git-svn-id: http://core.svn.wordpress.org/trunk@59601 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/update-core.php

@@ -1023,6 +1023,7 @@ $_new_bundled_files = array(
  * @global string[]           $_old_requests_files
  * @global string[]           $_new_bundled_files
  * @global wpdb               $wpdb                   WordPress database abstraction object.
+ * @global string             $wp_version             The WordPress version string.
  *
  * @param string $from New release unzipped path.
  * @param string $to   Path to old WordPress installation.

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.9-alpha-60264';
+$wp_version = '6.9-alpha-60265';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.