Bump Helm version to 2.16.0

The one we were installing wasn't compatible with the Kubernetes version
used by Kind.

Also, clean up the Helm installation since it's not included in the Flux
container.

Makefile

@@ -8,10 +8,10 @@ TEST_FLAGS?=
 BATS_COMMIT := 3a1c2f28be260f8687ff83183cef4963faabedd6
 SHELLCHECK_VERSION := 0.7.0
 SHFMT_VERSION := 2.6.4
+HELM_VERSION := 2.16.0
 
 include docker/kubectl.version
 include docker/kustomize.version
-include docker/helm.version
 include docker/sops.version
 
 # NB default target architecture is amd64. If you would like to try the
@@ -121,10 +121,9 @@ cache/%/kustomize-$(KUSTOMIZE_VERSION): docker/kustomize.version
 	curl --fail -L -o $@ "https://github.com/kubernetes-sigs/kustomize/releases/download/v$(KUSTOMIZE_VERSION)/kustomize_$(KUSTOMIZE_VERSION)_`echo $* | tr - _`"
 	[ $* != "linux-amd64" ] || echo "$(KUSTOMIZE_CHECKSUM)  $@" | shasum -a 256 -c
 
-cache/%/helm-$(HELM_VERSION): docker/helm.version
+cache/%/helm-$(HELM_VERSION):
 	mkdir -p cache/$*
 	curl --fail -L -o cache/$*/helm-$(HELM_VERSION).tar.gz "https://storage.googleapis.com/kubernetes-helm/helm-v$(HELM_VERSION)-$*.tar.gz"
-	[ $* != "linux-$(ARCH)" ] || echo "$(HELM_CHECKSUM_$(ARCH))  cache/$*/helm-$(HELM_VERSION).tar.gz" | shasum -a 256 -c
 	tar -m -C ./cache -xzf cache/$*/helm-$(HELM_VERSION).tar.gz $*/helm
 	mv cache/$*/helm $@