Add scroll to dropdowns

[stuzer05]

Description

If there're too many option in dropdowns, ui kinda breaks

Screenshots

Gitea Version

1.23.0+dev-300-g5791a73e75

Can you reproduce the bug on the Gitea demo site?

Yes

Operating System

No response

Browser Version

latest chrome

[wxiaoguang]

It seems to be a UI regression, the dropdown menu lost max-height limit.

(maybe not)