Docs: Add a `@since` note about `adjacent_posts_rel_link_wp_head()` no longer being used in core.

Follow-up to [48966].

Props jnylen0.
See #39111.
Built from https://develop.svn.wordpress.org/trunk@48995


git-svn-id: http://core.svn.wordpress.org/trunk@48757 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/link-template.php

@@ -1961,6 +1961,7 @@ function adjacent_posts_rel_link( $title = '%title', $in_same_term = false, $exc
  * or theme templates.
  *
  * @since 3.0.0
+ * @since 5.6.0 No longer used in core.
  *
  * @see adjacent_posts_rel_link()
  */

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-alpha-48994';
+$wp_version = '5.6-alpha-48995';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.