Makefile.docker: Fix example (#4868)

fix make example, remove stray comments
Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

Makefile.docker

@@ -14,9 +14,9 @@
 #
 # Testing docker is done e.g. via:
 #
-#  export DOCKER_PASSWORD=<pass>
+# export DOCKER_PASSWORD=<pass>
 # export DOCKER_LOGIN=miek
-# make DOCKER=miek -f Makefile.release release docker-push
+# make VERSION=x.y.z DOCKER=miek -f Makefile.docker release docker-push
 
 ifeq (, $(shell which curl))
     $(error "No curl in $$PATH, please install")
@@ -65,8 +65,6 @@ ifeq ($(DOCKER),)
 	$(error "Please specify Docker registry to use. Use DOCKER=coredns for releases")
 else
 	docker version
-	@# 1. Copy appropriate coredns binary to build/docker/linux/<arch>
-	@# 2. Copy Dockerfile to build/docker/linux/<arch>
 	for arch in $(LINUX_ARCH); do \
 	    docker build -t $(DOCKER_IMAGE_NAME)-$${arch}:$(VERSION) build/docker/$${arch}  && \
 	    docker tag $(DOCKER_IMAGE_NAME)-$${arch}:$(VERSION) $(DOCKER_IMAGE_NAME)-$${arch}:latest ;\