Revert "Rate-limit assets.digital.cabinet-office.gov.uk"
Revert "Rate-limit assets.digital.cabinet-office.gov.uk"

This reverts commit 7eb770985f7b02a950364a59edcaa79bda399315.

The `assets` virtual host is different to our `www.gov.uk` virtual host
in that it doesn't make use of the `real_ip_header` directive.

As such, the ratelimiting was applied to all requests coming from our
upstream vSE load balancer, i.e. the 10req/s limit was applied to all
requests, not per client IP address.

In practice this didn't cause a problem as most of our assets are cached
by Fastly; the few 429 errors we saw were most likely triggered by the
GOV.UK Crawler Worker.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet