minor #2335 [Site] Fix FileTree markup (minor) (smnandre)

This PR was merged into the 2.x branch.

Discussion
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[Site] Fix FileTree markup (minor)

Commits
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ceccf79 [Site] Fix FileTree markup (minor)

Author: smnandre

ux.symfony.com/templates/components/FileTree.html.twig

@@ -1,6 +1,6 @@
-<div class="FileTree FileTree-main list-unstyled px-3">
+<ul class="FileTree FileTree-main list-unstyled px-3">
     {{ _self.fileTree(files) }}
-</div>
+</ul>
 
 {% macro fileTree(files) %}
     {% for file_info in files %}