Use Cloudposse's repo for in the k8s image.

A lot of tools are packages there and saves a bit of a hassle.

images/k8s/Dockerfile

-FROM registry.hub.docker.com/library/golang:alpine3.14 as kind
-RUN GO111MODULE=on go get sigs.k8s.io/kind@v0.11.1
-
 FROM registry.hub.docker.com/library/alpine:3.14
-COPY --from=kind /go/bin/kind /usr/local/bin/
 # hadolint ignore=DL3018
-RUN apk add --update --no-cache --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing/ \
-        helm \
-        kubectl \
-    && \
+RUN wget -q https://apk.cloudposse.com/ops@cloudposse.com.rsa.pub -O /etc/apk/keys/ops@cloudposse.com.rsa.pub && \
+    echo "https://apk.cloudposse.com/3.14/vendor" >> /etc/apk/repositories && \
     apk add --update --no-cache \
         docker-cli \
+        helm \
+        kind \
+        kubectl \
     ;