Mark EKS 1.13 as deprecated

[sayboras]

Description

Fixes #2141

Created as draft PR, so that there will be no notification. Will send to review closing to 30th June.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Added labels for change area (e.g. area/nodegroup), target version (e.g. version/0.12.0) and kind (e.g. kind/improvement)
• Make sure the title of the PR is a good description that can go into the release notes

[martina-if]

Merge before Friday 26th so it's released with 0.23.0

[sayboras]

Merge before Friday 26th so it's released with 0.23.0

Thanks, let me set reminder for myself in slack 👍

[martina-if]

@sayboras I think we can already merge this since 0.22.0 was already branched out. Can you please rebase it? :)

[sayboras]

I think we can already merge this since 0.22.0 was already branched out. Can you please rebase it? :)

@martina-if Done 💯

[martina-if]

Manually tested and it works well 👍

./eksctl create cluster -f examples/01-simple-cluster.yaml 
[ℹ]  eksctl version 0.23.0-dev+8715a769.2020-06-18T14:57:51Z
[ℹ]  using region eu-north-1
Error: invalid version, 1.13 is no longer supported, supported values: 1.14, 1.15, 1.16
see also: https://docs.aws.amazon.com/eks/latest/userguide/kubernetes-versions.html

./eksctl create cluster --name martina-test-1-13-3 --version 1.13
[ℹ]  eksctl version 0.23.0-dev+8715a769.2020-06-18T14:57:51Z
[ℹ]  using region eu-north-1
Error: invalid version, 1.13 is no longer supported, supported values: 1.14, 1.15, 1.16
see also: https://docs.aws.amazon.com/eks/latest/userguide/kubernetes-versions.html