Change deb repo from http to https (#10173)

* Change deb repo from http to https

Given that http://apt.kubernetes.io/ is redirecting to https://packages.cloud.google.com/apt/ which is secure, then the suggestion is to change the source list to point to the correct destination.

* change apt source to https with apt.kubernetes.io

content/en/docs/setup/independent/install-kubeadm.md

@@ -128,7 +128,7 @@ For more information on version skews, please read our
 apt-get update && apt-get install -y apt-transport-https curl
 curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
 cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
-deb http://apt.kubernetes.io/ kubernetes-xenial main
+deb https://apt.kubernetes.io/ kubernetes-xenial main
 EOF
 apt-get update
 apt-get install -y kubelet kubeadm kubectl
@@ -251,7 +251,3 @@ If you are running into difficulties with kubeadm, please consult our [troublesh
 * [Using kubeadm to Create a Cluster](/docs/setup/independent/create-cluster-kubeadm/)
 
 {{% /capture %}}
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