Fix gitlab pages cache config
The current Gitlab Pages NGINX configuration is broken for GitLab Pages v0.5.0+
Pages specifies a Cache-Control header, which NGINX tries to respect, but the default proxy_cache_key value is unsuitable as it doesn't take hostname into account. So, https://foo.pages.io/index.html and https://bar.pages.io/index.html are both cached under the same key.
We didn't expect NGINX to be caching this data, and it adds no value, so disable it.
This should be picked into %9.5
Edited by Nick Thomas