Swapped nginx default annotations for their OpenShift HAProxy equivalents (#859)

Doc update

### Checklist

- [ ] Follow the [manual testing
process](https://github.com/sourcegraph/deploy-sourcegraph-helm/blob/main/TEST.md)
- [ ] Update
[changelog](https://github.com/sourcegraph/deploy-sourcegraph-helm/blob/main/charts/sourcegraph/CHANGELOG.md)
- [ ] Update [Kubernetes update
doc](https://docs.sourcegraph.com/admin/updates/kubernetes)

### Test plan

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Author: bailey-robbins-sg

charts/sourcegraph/examples/openshift/override.yaml

@@ -257,12 +257,16 @@ frontend:
 
   ingress:
     annotations:
-      # If using HAProxy router, add the timeout to prevent SSE / streaming timeouts
+      # Null out nginx defaults from values.yaml — not applicable
+      kubernetes.io/ingress.class: null
+      nginx.ingress.kubernetes.io/proxy-body-size: null
+      # HAProxy router: prevent SSE / streaming timeouts
       haproxy.router.openshift.io/timeout: 5m
-      kubernetes.io/ingress.class: openshift-default-example
-      nginx.ingress.kubernetes.io/proxy-body-size: 150m
-      # If terminating TLS on the router
+      # HAProxy router: equivalent of nginx proxy-body-size, for large Git pushes / file uploads
+      haproxy.router.openshift.io/request-body-size: 150m
+      # TLS termination at the router
       route.openshift.io/termination: edge
+    ingressClassName: openshift-default-example
     host: sourcegraph.example.com
 
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