Fixes https://github.com/go-gitea/gitea/issues/24326.
Set size class and downsize any such buttons that have a dropdown icon
because the dropdown icon increases button height artificially.
[`:has()`](https://developer.mozilla.org/en-US/docs/Web/CSS/:has) is not
supported in Firefox yet, but works fine with the experimental pref
enabled. I see this as a graceful degradation in unsupporting browsers.
75e35fb03a