Show only three significant digits in check execution time

fixes #8849

modules/monitoring/application/views/scripts/show/components/checkstatistics.phtml

@@ -68,7 +68,18 @@ if ($object->getType() === $object::TYPE_HOST) {
 <?php if ($object->check_execution_time): ?>
     <tr>
         <th><?= $this->translate('Check execution time') ?></th>
-        <td><?= $object->check_execution_time ?>s</td>
+        <td><?php
+            $matches = array();
+            if (preg_match(
+                '/(?<!.)([0-9]+\.[0-9]{4,})(?!.)/ms',
+                $object->check_execution_time,
+                $matches
+            )) {
+                printf('%.3f', (float) $matches[1]);
+            } else {
+                echo $object->check_execution_time;
+            }
+        ?>s</td>
     </tr>
 <?php endif ?>
 <?php if ($object->check_latency): ?>