Updated to new location for Helm stable repository

Description

https://kubernetes-charts.storage.googleapis.com is end of line as of November 13, 2020. New location for stable repository is https://charts.helm.sh/stable. Announcement from Helm available at https://helm.sh/blog/new-location-stable-incubator-charts/

How Has This Been Tested?

~$ helm version WARNING: Kubernetes configuration file is group-readable. This is insecure. Location: /root/kubeconfig-k3s-alpine WARNING: Kubernetes configuration file is world-readable. This is insecure. Location: /root/kubeconfig-k3s-alpine WARNING: "kubernetes-charts.storage.googleapis.com" is deprecated for "stable" and will be deleted Nov. 13, 2020. WARNING: You should switch to "https://charts.helm.sh/stable" via: WARNING: helm repo add "stable" "https://charts.helm.sh/stable" --force-update version.BuildInfo{Version:"v3.4.1", GitCommit:"c4e74854886b2efe3321e185578e6db9be0a6e29", GitTreeState:"clean", GoVersion:"go1.14.11"}

~$ helm repo add "stable" "https://charts.helm.sh/stable" --force-update WARNING: Kubernetes configuration file is group-readable. This is insecure. Location: /root/kubeconfig-k3s-alpine WARNING: Kubernetes configuration file is world-readable. This is insecure. Location: /root/kubeconfig-k3s-alpine WARNING: "kubernetes-charts.storage.googleapis.com" is deprecated for "stable" and will be deleted Nov. 13, 2020. WARNING: You should switch to "https://charts.helm.sh/stable" via: WARNING: helm repo add "stable" "https://charts.helm.sh/stable" --force-update "stable" has been added to your repositories

~$ helm repo update WARNING: Kubernetes configuration file is group-readable. This is insecure. Location: /root/kubeconfig-k3s-alpine WARNING: Kubernetes configuration file is world-readable. This is insecure. Location: /root/kubeconfig-k3s-alpine Hang tight while we grab the latest from your chart repositories... ...Successfully got an update from the "ingress-nginx" chart repository ...Successfully got an update from the "portainer" chart repository ...Successfully got an update from the "jetstack" chart repository ...Successfully got an update from the "openfaas" chart repository ...Successfully got an update from the "stable" chart repository

Checklist:

I have:

[X] checked my changes follow the style of the existing code / OpenFaaS repos
[X] updated the documentation and/or roadmap in README.md
[X] read the CONTRIBUTION guide
[X] signed-off my commits with git commit -s
[ ] added unit tests

openfaas / ofc-bootstrap