Docs: Clarify the file header for wp-includes/class-walker-category-dropdown.php, introduced in [34110].

Also clarifies the class DocBlock and tags for `Walker_CategoryDropdown`.

See #33413. See #33701.


git-svn-id: https://develop.svn.wordpress.org/trunk@34417 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-walker-category-dropdown.php

@@ -1,17 +1,18 @@
 <?php
 /**
- * Category API: Walker_CategoryDropdown class
+ * Taxonomy API: Walker_CategoryDropdown class
  *
  * @package WordPress
  * @subpackage Template
+ * @since 4.4.0
  */
 
 /**
- * Create HTML dropdown list of Categories.
+ * Core class used to create an HTML dropdown list of Categories.
  *
- * @package WordPress
  * @since 2.1.0
- * @uses Walker
+ *
+ * @see Walker
  */
 class Walker_CategoryDropdown extends Walker {
 	/**