Refactor Files Header to use `gl-` utility classes
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The files header component is currently using custom styles. Let's move away from that and apply `gl-` util classes on the components.
Make sure to address these too:
- [ ] @zcuddy started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/46406#note_441859388): (+1 comment)
> **question:** Are we able to utilize utility classes to replace this custom style? I'm worried that it doesn't fit our [GitLab UI spacing scale](https://gitlab.com/gitlab-org/gitlab-ui/-/blob/master/src/scss/variables.scss#L4-20)
- [ ] @zcuddy started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/46406#note_441859384):
> **question:** Are we able to utilize utility classes to replace this custom style? I'm worried that it doesn't fit our [GitLab UI spacing scale](https://gitlab.com/gitlab-org/gitlab-ui/-/blob/master/src/scss/variables.scss#L4-20)
## Note
There are a few areas of our app using `file-headers`, so please make sure to make the changes on **ALL** of them.
issue