Accessibility: Fix `ButtonLink` blocking focus

Created by: umpox

Description

Regression introduced in https://github.com/sourcegraph/sourcegraph/pull/36205/files#diff-7b82add34f7d69e33598ffbe9b19076f246d0aea3f072b9dd6a1058016eb4a6cR15

We only want to preventDefault if we are overriding this behavior to force a click (e.g. override Space behavior to click instead of jump scroll down the page)

Test plan

Tested locally using a keyboard

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.