Themes: Remove caching todo from get_uploaded_header_images().

Remove the note to introduce caching to `get_uploaded_header_images()` as caching has since been introduced to `WP_Query` and therefore `get_posts()`. The comment is out of date.

Props audrasjb, desrosj, flixos90, mukesh27, pbearne, pbiron, sachinrajcp123, sergeybiryukov, swissspidy, westonruter, whyisjake.
See #49446, #63168.


git-svn-id: https://develop.svn.wordpress.org/trunk@60979 602fd350-edb4-49c9-b593-d223f7449a82

Author: peterwilsoncc

src/wp-includes/theme.php

@@ -1500,7 +1500,6 @@ function header_image() {
 function get_uploaded_header_images() {
 	$header_images = array();
 
-	// @todo Caching.
 	$headers = get_posts(
 		array(
 			'post_type'  => 'attachment',