release-20.1: server: Apply cookie auth to /debug/ endponts

Jesse Seldess commented:


PR: https://github.com/cockroachdb/cockroach/pull/50487

From release notes:
> HTTP endpoints beginning with `/debug/` now require a valid [`admin`](../v20.1/authorization.html] login session. [#50487][#50487) {% comment %}doc{% endcomment %}

Jira Issue: DOC-583