fix(xss): close double-quoted string in aggregate graph_list block

The graph_list interpolation change left the prior single-quote close, leaving
the string opened at the <p> segment unterminated and breaking graphs.php with
a parse error. Close with a double quote to match the sibling itemlist blocks.

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

Author: somethingwithproof

graphs.php

@@ -1008,7 +1008,7 @@ function form_actions() {
 				print "<td class='textArea'>
 					<p>" . __('Click \'Continue\' to create an Aggregate Graph from the selected Graph(s).'). "</p>
 					<div class='itemlist'><ul>$graph_list</ul></div>
-				</td></tr>';
+				</td></tr>";
 
 				/* list affected data sources */
 				print '<tr>';