Add target to the board card component's labels

What does this MR do and why?

Integration MR for feat(GlLabel): render label as text when target... (gitlab-ui!2864 - merged).

This MR adds a target to the board card component so that it has :hover styles. See gitlab-ui!2864 (comment 975499394) for more context.

Screenshots or screen recordings

When gitlab-ui!2864 (merged) is applied.

Current (no target)	After (with target)

How to set up and validate locally

1. View a group's epic board at: http://localhost:3000/groups/gitlab-org/-/epic_boards
2. If an issue doesn't have labels add some using the sidebar by clicking on the issue card.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.