In `core_upgrade_preamble()`, `$alternate` is set then never used.

See #27882.

Built from https://develop.svn.wordpress.org/trunk@28314


git-svn-id: http://core.svn.wordpress.org/trunk@28142 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/update-core.php

@@ -182,7 +182,6 @@ function core_upgrade_preamble() {
 	}
 
 	echo '<ul class="core-updates">';
-	$alternate = true;
 	foreach( (array) $updates as $update ) {
 		echo '<li>';
 		list_core_update( $update );