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.



git-svn-id: https://develop.svn.wordpress.org/trunk@43463 602fd350-edb4-49c9-b593-d223f7449a82

src/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
 	 */