Fix scoped label styles in activity feed

What does this MR do and why?

Describe in detail what your merge request does and why.

Makes scoped labels display with a border in the project & group activity feeds.

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Premium or higher licence needed. Learn more about developer licences for working on GitLab EE.
2. Create a scoped label. For example scoped::label.
3. Add a comment that includes the scoped label to an issue, on a project in a group. For example This is my ~scoped::label comment on http://127.0.0.1:3000/flightjs/Flight/-/issues/9.
4. View the comment on the project activity feed. It can take up to 15min for the activity to show. For example http://127.0.0.1:3000/flightjs/Flight/activity.
5. View the comment on the group activity feed. It can take up to 15min for the activity to show. For example http://127.0.0.1:3000/groups/flightjs/-/activity.

MR acceptance checklist

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