Backport: Avoid redirect loop from archived pages [v17.8]

What does this MR do and why?

Avoids the redirect loop on the 404 page for version 17.8.

Versions prior to 17.9 are no longer hosted on docs.gitlab.com, so we no longer need this redirect at all (17.8 is already on the archives site).

The redirect becomes problematic when deployed to archives.docs.gitlab.com, where it causes the 404 to redirect back to itself in a loop.

This (plus a similar MR for v17.7) will close gitlab-org/technical-writing/docs-gitlab-com#278 (closed).

How to set up and validate locally

Can't easily validate locally. We'll just test on prod.

It's safe to assume this will work since we're removing the include for the file that yielded the problematic behavior on the archives site.

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