Update CHART_VERSIONS for GitLab Chart release v5.6.0

Created by pipeline: https://dev.gitlab.org/gitlab/charts/gitlab/-/pipelines/221443

Summary

Original MR changes

• Updates to Chart version 5.6.0
• Drops Chart version 5.3.6

Additional MR changes

• Updates NGINX RBAC configuration per changes from gitlab-org/charts/gitlab!2267 (merged)
• Adds NGINX IngressClass manifest (https://kubernetes.io/docs/concepts/services-networking/ingress/#ingressclass-scope)
• Only sets NGINX annotations on MinIO ingress if global.ingress.provider=nginx
• MinIO Ingress replaces kubernetes.io/ingress.class with spec.ingressClassName
• No longer includes networking.k8s.io/v1beta1 in Helm's IngressSelector
• Automatically sets NGINX's Service LoadBalancerIP using global.hosts.externalIP (workaround until gitlab-org/charts/gitlab!2317 (merged) is released in 5.6.1 - see #513 (closed))

Testing

• Full pipeline: https://gitlab.com/gitlab-org/cloud-native/gitlab-operator/-/pipelines/435324259 ✅
• Did a manual install and upgrade from 5.5.2 to 5.6.0 and all worked as expected ✅