Docs: Correct @since value for _wp_privacy_statuses().

Fix typo in `@since` entry for `WP_Privacy_Policy_Content:add()`.

Props dimadin.
Fixes #44915.

git-svn-id: https://develop.svn.wordpress.org/trunk@43638 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/post.php

@@ -859,7 +859,7 @@ function get_page_statuses() {
 /**
  * Return statuses for privacy requests.
  *
- * @since 5.0.0
+ * @since 4.9.6
  *
  * @return array
  */