Commits Author filter button doesn't conform to Pajamas specs

The ability to filter commits by Author was introduced in !28509 (merged). The UX that was approved can be seen in the description of that MR. But what is found in production differs from that:

Approved	Actual, on GitLab.com

There seems to be a “halo” effect around the Author button. The different height, compared to the text input on the right, was fixed in !31686 (merged).