Follow-up from "Allow to enable a performance bar with the `p b` keyboard shortcut"

The following discussion from gitlab-ce!11439 should be addressed:

• @ClemMakesApps started a discussion: (+1 comment)

  Can we use a button here instead of a blank anchor link?

Since I've copied that from app/views/help/_shortcuts.html.haml we'll need to fix both at once.