Docs: Clarify the class DocBlock summary for WP_Screen.

See #32246.


git-svn-id: https://develop.svn.wordpress.org/trunk@34422 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/class-wp-screen.php

@@ -8,10 +8,9 @@
  */
 
 /**
- * A class representing the admin screen.
+ * Core class used to implement an admin screen API.
  *
  * @since 3.3.0
- * @access public
  */
 final class WP_Screen {
 	/**