Update to maintained version of docker-registry chart

As part of the deprecation of the "stable" Helm charts, the chart
`stable/docker-registry` has been deprecated explicitly:
helm/charts#24303

In particular, this chart no longer builds successfully, and the version
that we had pinned to doesn't work with the latest Kubernetes:

```
stderr: 'Error: unable to build kubernetes objects from release
manifest: unable to recognize "": no matches for kind "Ingress" in
version "extensions/v1beta1"'
```

This commit swaps to using the chart pointed to at
https://artifacthub.io/packages/helm/twuni/docker-registry, which
appears to be the most actively maintained chart following the
deprecation of the original.

We may want to consider building our own at some point though...

roles/k8s-internal-container-registry/defaults/main.yml

@@ -1,16 +1,16 @@
 ---
 helm_cmd: "/usr/local/bin/helm"
 
-container_registry_chart_location: "https://charts.helm.sh/stable"
-container_registry_repo_name: "stable"
+container_registry_chart_location: "https://helm.twun.io"
+container_registry_repo_name: "twuni"
 container_registry_chart_name: "{{ container_registry_repo_name }}/docker-registry"
 container_registry_installed_name: "docker-registry"
 
 container_registry_values_template: "values.yaml"
 container_registry_values_path: "/tmp/container-registry.yaml"
 
 container_registry_namespace: "deepops-docker"
-container_registry_version: 1.9.4
+container_registry_version: "2.1.0"
 container_registry_hostname: registry.local
 container_registry_ingress_enabled: false
 container_registry_ingress_size: 4096m

roles/k8s-internal-container-registry/templates/values.yaml

@@ -13,8 +13,8 @@ ingress:
   enabled: "{{ container_registry_ingress_enabled }}"
   hosts:
   - "{{ container_registry_hostname }}"
+  className: "nginx"
   annotations:
-    kubernetes.io/ingress.class: "nginx"
     nginx.ingress.kubernetes.io/ssl-redirect: "false"
     nginx.ingress.kubernetes.io/rewrite-target: /
     nginx.ingress.kubernetes.io/proxy-body-size: "{{ container_registry_ingress_size }}"