Clarifies which browser versions we support

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/169621



Merged-by: Evan Read <eread@gitlab.com>
Approved-by: Peter Hegman <phegman@gitlab.com>
Approved-by: Evan Read <eread@gitlab.com>
Co-authored-by: Sam Beckham <sbeckham@gitlab.com>