Docs: Add missing function documentation for list_plugin_updates().

Introduced in [9543].

Props priyankkpatel, mukesh27.
Fixes #47424.

git-svn-id: https://develop.svn.wordpress.org/trunk@45480 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/update-core.php

@@ -241,6 +241,11 @@ function core_upgrade_preamble() {
 	dismissed_updates();
 }
 
+/**
+ * Display the upgrade plugins form.
+ *
+ * @since 2.7.0
+ */
 function list_plugin_updates() {
 	$wp_version     = get_bloginfo( 'version' );
 	$cur_wp_version = preg_replace( '/-.*$/', '', $wp_version );