Tests: Use multi-line block comment style in get_feed_build_date test.

Follow WordPress inline documentation standards section 5.2 — multi-line
comments use /* */ with leading asterisks, not repeated //.

Addresses follow-up feedback from @westonruter.

Props westonruter.

See #59956.

Author: chubes4

tests/phpunit/tests/date/getFeedBuildDate.php

@@ -57,10 +57,12 @@ public function test_should_not_error_when_modified_times_is_empty() {
 			)
 		);
 
-		// Use a query where have_posts() is true but wp_list_pluck()
-		// returns an empty array because the posts array contains scalar
-		// values (neither objects nor arrays). This triggers the _doing_it_wrong
-		// notice in WP_List_Util::pluck() and produces an empty result.
+		/*
+		 * Use a query where have_posts() is true but wp_list_pluck()
+		 * returns an empty array because the posts array contains scalar
+		 * values (neither objects nor arrays). This triggers the _doing_it_wrong
+		 * notice in WP_List_Util::pluck() and produces an empty result.
+		 */
 		query_posts(
 			array(
 				'posts__in' => array( $id ),