Update Duo Workflow user docs to dockerless

Problem

With LS: Switch to Dockerless by default and only di... (gitlab-org/editor-extensions/gitlab-lsp#810 - closed), Duo Workflow in the IDE will by default run without Docker, but the user docs s still reference Docker.

Desired Outcome

User facing docs are clarified that Duo Workflow works by default without Docker. This includes warnings around security.

Doc should still mention Docker execution as alternative solution for the time being.