webui: Changed alert rule triggered icon from X to ! (#8760)

![image](https://user-images.githubusercontent.com/39462/40490177-981b5a78-5f30-11e8-949d-2353272b334b.png)


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html/includes/print-alert-rules.php

@@ -131,7 +131,7 @@ foreach (dbFetchRows($full_query, $param) as $rule) {
             $ico = 'check';
             $col = 'success';
         } elseif ((int) $sub['state'] === 1 || (int) $sub['state'] === 2) {
-            $ico   = 'remove';
+            $ico   = 'exclamation';
             $col   = 'danger';
             $extra = 'danger';
         }