Drop the eks. subdomain from govuk.digital. domains

[theseanything]

Very low priority enhancement. As we no longer are two sets of infrastructure in parallel, having the eks. subdomain for our govuk.digital. domains isn't very useful. We don't need to distinguish between sets of infrastructure, nor do we really need to know that it's host on EKS.

We could simplify domains for example:

argo.eks.integration.govuk.digital -> argo.integration.govuk.digital

Saves a few extra keystrokes when filling in a URL (particularly before autocomplete kicks in for the environment).

Realise that this might be high effort/risk vs value, due to things like Dex callback URLs, CDN config etc etc.