revert: fix(GlButton): use safe link directive

What does this MR do?

Reverts !2155 (merged) because the safe-link directive escapes data URLs, which is needed for the 2FA recovery codes download button: app/assets/javascripts/authentication/two_factor_auth/components/recovery_codes.vue. We had a pipeline failure as a result of the change: https://gitlab.com/gitlab-renovate-forks/gitlab/-/jobs/1204022287

We might need to expose a special prop to allow "unsafe URLs" in some cases. TBD.

/cc @djadmin