Docs: Add deprecation note for $use_cache in get_site_option().

Props johnbillion.
See #28290.

Built from https://develop.svn.wordpress.org/trunk@34779


git-svn-id: http://core.svn.wordpress.org/trunk@34744 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/option.php

@@ -975,6 +975,7 @@ function delete_all_user_settings() {
  * Retrieve an option value for the current network based on name of option.
  *
  * @since 2.8.0
+ * @since 4.4.0 The `$use_cache` parameter was deprecated.
  * @since 4.4.0 Modified into wrapper for get_network_option()
  *
  * @see get_network_option()