Bump nginx config

What does this MR do and why?

This is a follow-up to !64 (merged). It turned out that we forgot to update deployment attributes to force pod recreation so that it starts using the new container name.

This MR changes the deployment nginx config, which will force the pod(s) to be recreated.

This will unblock Add zoekt-gateway to fluentd (gitlab-com/gl-infra/k8s-workloads/tanka-deployments!821 - merged)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Check out v0.8.1 (Version before we renamed zoekt-gateway container)

   git checkout v0.8.1

2. Install the chart

   helm install gitlab-zoekt .

3. Describe the deployment pod. For example, kubectl describe po gitlab-zoekt-gateway-7b6f8cbb4d-jvf9n
4. Ensure that container name is zoekt-gateway
5. Check out this MR's branch
6. Upgrade the chart

   helm upgrade gitlab-zoekt .

7. Describe the deployment pod again. This time the container name should be zoekt-external-gateway