Test if experimentalRetryJoin still needed for K8s 1.19+

[jsturtevant]

/kind feature

Describe the solution you'd like
In 1.19+ retry support was added to kubeadm: https://kubernetes.slack.com/archives/C8TSNPY4T/p1601486982126900. We should test 1.19 to see if the useExperimentalRetryJoin is still required as was added for #832 and #833.

Anything else you would like to add:
This is related to kubernetes-sigs/cluster-api-provider-aws#1993 and Window support kubernetes-sigs/cluster-api#3616 (comment)

Environment:

• cluster-api-provider-azure version:
• Kubernetes version: (use kubectl version): 1.19+
• OS (e.g. from /etc/os-release):

[nader-ziada]

/assign