Update digital ocean kubernetes cluster slug
This fixes invalid slug version
due to
doctl kubernetes options versions
Slug Kubernetes Version
1.19.3-do.2 1.19.3
1.18.10-do.2 1.18.10
1.17.13-do.2 1.17.13
This fixes invalid slug version
due to
doctl kubernetes options versions
Slug Kubernetes Version
1.19.3-do.2 1.19.3
1.18.10-do.2 1.18.10
1.17.13-do.2 1.17.13