Docs: Add missing description for $wp_query and $wp_the_query globals.

Props mukesh27.
See #45604, #47110.

git-svn-id: https://develop.svn.wordpress.org/trunk@45739 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/post-thumbnail-template.php

@@ -83,7 +83,7 @@ function the_post_thumbnail( $size = 'post-thumbnail', $attr = '' ) {
  *
  * @since 3.2.0
  *
- * @global WP_Query $wp_query
+ * @global WP_Query $wp_query WordPress Query object.
  *
  * @param WP_Query $wp_query Optional. A WP_Query instance. Defaults to the $wp_query global.
  */