REST API: Fix some incorrect @since tags.

[43437] included some new methods, which were incorrectly tagged as being `@since 4.9.7`. This updates them to `4.9.8`.

Props danielbachhuber.
Fixes 44287.


Built from https://develop.svn.wordpress.org/trunk@43463


git-svn-id: http://core.svn.wordpress.org/trunk@43290 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

@@ -1757,7 +1757,7 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 	/**
 	 * Get the link relations available for the post and current user.
 	 *
-	 * @since 4.9.7
+	 * @since 4.9.8
 	 *
 	 * @param WP_Post $post Post object.
 	 * @param WP_REST_Request Request object.
@@ -2160,7 +2160,7 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 	/**
 	 * Retrieve Link Description Objects that should be added to the Schema for the posts collection.
 	 *
-	 * @since 4.9.7
+	 * @since 4.9.8
 	 *
 	 * @return array
 	 */