Remove some unused globals and/or their docs.

See ##33491.


git-svn-id: https://develop.svn.wordpress.org/trunk@34446 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/post-template.php

@@ -528,13 +528,12 @@ function body_class( $class = '' ) {
  * @since 2.8.0
  *
  * @global WP_Query $wp_query
- * @global wpdb     $wpdb
  *
  * @param string|array $class One or more classes to add to the class list.
  * @return array Array of classes.
  */
 function get_body_class( $class = '' ) {
-	global $wp_query, $wpdb;
+	global $wp_query;
 
 	$classes = array();