minor #9904 [Filesystem] Improved the code of an example (javiereguiluz)

This PR was merged into the 2.8 branch.

Discussion
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[Filesystem] Improved the code of an example

This continues #9903 and removes the last `mt_rand()` example in the docs.

Commits
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35e98e6 [Filesystem] Improved the code of an example

Author: javiereguiluz

components/filesystem.rst

@@ -34,7 +34,7 @@ endpoint for filesystem operations::
     $fileSystem = new Filesystem();
 
     try {
-        $fileSystem->mkdir('/tmp/random/dir/'.mt_rand());
+        $fileSystem->mkdir(sys_get_temp_dir().'/'.random_int(0, 1000));
     } catch (IOExceptionInterface $exception) {
         echo "An error occurred while creating your directory at ".$exception->getPath();
     }