fix(helm): omit api-server replicas when HPA is enabled (#62052)

* fix(helm): omit api-server replicas when HPA is enabled

When apiServer.hpa.enabled is true, the deployment must not set a
replicas field so the HPA can manage replica count. Otherwise GitOps
tools (e.g. ArgoCD) detect drift and continuously reconcile.

Follows the same pattern used by webserver and workers deployments.

* Addressing PR comments about default version tests.