archiving(1.1) exclude: remove version 1.1, part 1: reviewable steps

[pepopowitz]

BLOCKED: by the unsupported/1.1 site not being in production yet.

Description

Part of #2186.

Includes the smaller items for removing version 1.1 from the main docs, to keep the PR in a reviewable state.

Included in this PR

• Remove 1.1 from the version manifest file, so that it's not included in the deployed site

• Redirect all 1.1 traffic to unsupported.docs.camunda.io/1.1 (or stage.unsupported.docs.camunda.io/1.1 for the staging build)

• Move 1.1 to the "Unsupported versions" sub-list in the top nav version selector, redirecting to unsupported.docs.camunda.io/1.1:

  

When should this change go live?

• I intend to merge this on Friday, Aug 11, after I've deployed the unsupported/1.1 site to production.
• This change is not yet live and should not be merged until {ADD_DATE} (apply hold label or convert to draft PR)?
• There is no urgency with this change.
• This change or page is part of a marketing blog, conference talk, or something else on a schedule.
• This functionality is already available but undocumented.
• This is a bug fix or security concern.

PR Checklist

• I have added changes to the relevant /versioned_docs directory, or they are not for an already released version.
• I have added changes to the main /docs directory (aka /next/), or they are not for future versions.
• My changes require an Engineering review, and I've assigned an engineering manager or tech lead as a reviewer, or my changes do not require an Engineering review.
• My changes require a technical writer review, and I've assigned @christinaausley as a reviewer, or my changes do not require a technical writer review.

[akeller]

Changes as expected 🚀