minor symfony#9318 [PHPUnit Bridge] fixing second stopwatch example (chr-hertel)

This PR was merged into the 2.8 branch.

Discussion
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[PHPUnit Bridge] fixing second stopwatch example

follow up to symfony#7856

Commits
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02ff5f6 fixing second stopwatch example in phpunit-bridge docs

Author: xabbuh

components/phpunit_bridge.rst

@@ -232,11 +232,11 @@ test::
         {
             $stopwatch = new Stopwatch();
 
-            $stopwatch->start();
+            $stopwatch->start('event_name');
             sleep(10);
-            $duration = $stopwatch->stop();
+            $duration = $stopwatch->stop('event_name')->getDuration();
 
-            $this->assertEquals(10, $duration);
+            $this->assertEquals(10000, $duration);
         }
     }