gl-button link hover text underline is cut off in Firefox
The text underline for `gl-button` link is cut off in Firefox
| Browser | With `overflow: hidden` (current) | Without `overflow: hidden (proposal) |
| ------ | ------ | ------ |
| ❌ Firefox |  |  |
| ✅ Chrome |  |  |

## More Information
- [ ] @pedroms started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38733#note_392546715): (+2 comments)
> @sming-gitlab 🎨 **Style**: the `overflow: hidden` in the `.gl-button-text` around the `Show more` text is cutting part of its underline when hovering:
>
> | With `overflow: hidden` | Without `overflow: hidden` |
> |---|---|
> |  |  |
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38733#note_392751552
> @mvanremmerden: This seems to be a Firefox problem. It looks fine to me on Safari and Chrome, but on Firefox I'm seeing the same thing as
> 
issue