ingress: Try disabling nginx buffering

It seems like nginx's proxy request buffering is causing us issues on Windows where we can't reliably clone the repo. Try to see if we can make do without it, and if that improves anything.

After deciding on this and googling around, it looks like nginx upstream do the same for Gitaly ops, but would prefer not to do it for the API. Unfortunately, it doesn't seem like there's a good way to select on the two: https://gitlab.com/gitlab-org/charts/gitlab/-/issues/2262 and https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/4010

For now, just disable buffering altogether, and hope the impact isn't too bad.

Signed-off-by: Daniel Stone daniels@collabora.com