[bug] Kubernetes version specifed in qhub-config.yaml not respected (AWS deployments)

[iameskild]

Describe the bug

A clear and concise description of what the problem is.

Kubernetes version specified on qhub-config.yaml is not respected for AWS deployment.

In qhub-config.yaml:

amazon_web_services:
  region: us-west-2
  kubernetes_version: '1.18'

And from EKS:

$ kubernetes version
...
Server Version: version.Info{Major:"1", Minor:"21+", GitVersion:"v1.21.2-eks-0389ca3", GitCommit:"8a4e27b9d88142bbdd21b997b532eb6d493df6d2", GitTreeState:"clean", BuildDate:"2021-07-31T01:34:46Z", GoVersion:"go1.16.5", Compiler:"gc", Platform:"linux/amd64"

Your environment

Describe the environment in which you are experiencing the bug.

Include your conda version (use conda --version), k8s and any other relevant details.

$ conda --version
conda 4.10.1

$ conda list
# packages in environment at /Users/eskild/miniconda3/envs/qhub-0.3.12:
#
# Name                    Version                   Build  Channel
...
python                    3.9.7                h88f2d9e_1
...
qhub                      0.3.12                   pypi_0    pypi
...