Update minimum extension version in Duo Workflow docs

What does this MR do and why?

Updates Duo Workflow documentation to change minimum required extension version.

It's because we're introducing a breaking change. Since this feature is still in experiment phase, it's not a problem to introduce breaking changes but we need to update the docs so users can use the correct version of the VSCode extension and keep using Duo Workflow. See this thread FYI.

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Before	After

How to set up and validate locally

1. Visit http://main-ee-170414.docs.gitlab-review.app/ee
2. See changes in the duo workflow docs