Merge branch 'ST-456-upgrade-kubectl' into 'st-456-refactor-tests'

Upgraded kubectl just to see if this works

See merge request ska-telescope/ska-docker!37

docker/deploy/.release

-release=0.4.2
-tag=deploy-0.4.2
+release=0.4.3
+tag=deploy-0.4.3

docker/deploy/Dockerfile

 FROM ubuntu:18.04
 
-ENV KUBE_LATEST_VERSION="v1.16.2"
+ENV KUBE_LATEST_VERSION="v1.18.2"
 ENV HELM_VERSION="v3.3.1"
 ENV DEBIAN_FRONTEND="noninteractive"
 ENV RUNLEVEL="1"