Forking page branch selection dropdown list overflow when a long content item is selected.

[lunny]

[wxiaoguang]

I think you need to take a look at the devtest page, instead of copying the unclear legacy frontend code.

Screenshot:

[wxiaoguang]

This is the related PR you have reviewed and approved: Fix some UI problems (dropdown/container) (#30849)

[lunny]

The example bug comes from the forking page.