chart: core-provider remove inconsistent pre-delete hook (#858)

In #454 the pre-delete hook was removed from the Namespace and in #508
it was removed from the CAPIProvider

However the pre-delete hook remains on the ConfigMap, which means if
installation fails for any reason prior to creating the Namespace in
the post-install hook, the chart can become undeletable with an error
like:

+ helm_v3 uninstall rancher-turtles --namespace rancher-turtles-system --wait
Error: warning: Hook pre-delete rancher-turtles/templates/core-provider.yaml failed: 1 error occurred:
	* namespaces "capi-system" not found

charts/rancher-turtles/templates/core-provider.yaml

@@ -54,7 +54,7 @@ metadata:
   name: capi-additional-rbac-roles
   namespace: {{ index .Values "cluster-api-operator" "cluster-api" "core" "namespace" }}
   annotations:
-    "helm.sh/hook": "post-install, post-upgrade, pre-delete"
+    "helm.sh/hook": "post-install, post-upgrade"
     "helm.sh/hook-weight": "2"
 data: 
   manifests: |-