minor #17529 [Stopwatch] add precision for stopwatch getEvent function (MrYamous)

This PR was merged into the 5.4 branch.

Discussion
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[Stopwatch] add precision for stopwatch getEvent function

This is not a big problem but I find this example confusing as getEvent() function from Stopwatch must have an event name as parameter

Commits
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5cf6f9e add precision for stopwatch getEvent function

Author: javiereguiluz

performance.rst

@@ -278,7 +278,7 @@ information about the current event, even while it's still running. This
 object can be converted to a string for a quick summary::
 
     // ...
-    dump((string) $this->stopwatch->getEvent()); // dumps e.g. '4.50 MiB - 26 ms'
+    dump((string) $this->stopwatch->getEvent('export-data')); // dumps e.g. '4.50 MiB - 26 ms'
 
 You can also profile your template code with the :ref:`stopwatch Twig tag <reference-twig-tag-stopwatch>`: