Docs: Add missing descriptions for the $wpdb global in DocBlocks all the places.

See #32246.


git-svn-id: https://develop.svn.wordpress.org/trunk@35170 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/author-template.php

@@ -319,7 +319,7 @@ function get_author_posts_url($author_id, $author_nicename = '') {
  *
  * @since 1.2.0
  *
- * @global wpdb $wpdb
+ * @global wpdb $wpdb WordPress database abstraction object.
  *
  * @param string|array $args {
  *     Optional. Array or string of default arguments.
@@ -453,7 +453,7 @@ function wp_list_authors( $args = '' ) {
  *
  * @since 3.2.0
  *
- * @global wpdb $wpdb
+ * @global wpdb $wpdb WordPress database abstraction object.
  *
  * @return bool Whether or not we have more than one author
  */