Consider dropping deploy preview support for redirects app

[jchristgit]

Do we need previews of the legacy redirects?

If not, we may be able to remove a lot of code from the redirects app.

[jchristgit]

@HassanAbouelela do you know if we can action this issue somehow?

[HassanAbouelela]

Part of the issue is we use some redirects even within the main site, particularly in things like nav. Removing the redirects from static builds makes parts of the site non-functional.

[jchristgit]

Does this still apply if we fix #681 ?

[HassanAbouelela]

It would definitely resolve the issue in the short term, but we'd encounter the same issue in the future if we change other links.