General: Add missing closing li in plugin editor.

Adds a missing closing `li` tag in the plugin editor file list.

Props dkarfa, pmbaldha, sandeepdahiya, cikrimcin, westonruter, audrasjb, joedolson.
Fixes #63546.

git-svn-id: https://develop.svn.wordpress.org/trunk@60479 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-admin/plugin-editor.php

@@ -288,6 +288,7 @@
 		<ul role="group">
 			<?php wp_print_plugin_file_tree( wp_make_plugin_file_tree( $plugin_editable_files ) ); ?>
 		</ul>
+	</li>
 	</ul>
 </div>