chore(rootfs/Dockerfile): update Helm to v2.16.12 (#252)

See https://github.com/helm/helm/releases/tag/v2.16.12

Author: mboersma

rootfs/Dockerfile

@@ -8,7 +8,7 @@ ENV AZCLI_VERSION=2.12.1 \
     GO_VERSION=1.15.2 \
     GLIDE_VERSION=v0.13.3 \
     GLIDE_HOME=/root \
-    HELM_VERSION=v2.16.9 \
+    HELM_VERSION=v2.16.12 \
     KUBECTL_VERSION=v1.16.3 \
     ETCDCTL_VERSION=v3.1.8 \
     GOLANGCI_LINT_VERSION=v1.31.0 \