remove makefile for building container image (superseded by pipeline pushing to ghcr.io)

https://github.com/fphammerle/docker-postfix/commit/56b31b509f44c376ac199c96655b08f5c079997b

Makefile

@@ -1,23 +0,0 @@
-# sync with https://github.com/fphammerle/docker-onion-service/blob/master/Makefile
-
-DOCKER_IMAGE_NAME := docker.io/fphammerle/postsrsd
-DOCKER_TAG_VERSION := $(shell git describe --match=0.* --abbrev=0 --dirty | sed -e 's/^v//')
-POSTSRSD_PACKAGE_VERSION := $(shell grep -Po 'POSTSRSD_PACKAGE_VERSION=\K.+' Dockerfile | tr -d -)
-ARCH := $(shell arch)
-DOCKER_TAG_ARCH_SUFFIX_aarch64 := arm64
-DOCKER_TAG_ARCH_SUFFIX_armv6l := armv6
-DOCKER_TAG_ARCH_SUFFIX_x86_64 := amd64
-DOCKER_TAG_ARCH_SUFFIX = ${DOCKER_TAG_ARCH_SUFFIX_${ARCH}}
-DOCKER_TAG = ${DOCKER_TAG_VERSION}-postsrsd${POSTSRSD_PACKAGE_VERSION}-${DOCKER_TAG_ARCH_SUFFIX}
-
-.PHONY: docker-build docker-push
-
-docker-build:
-	git diff --exit-code
-	git diff --staged --exit-code
-	sudo docker build -t "${DOCKER_IMAGE_NAME}:${DOCKER_TAG}" .
-
-docker-push: docker-build
-	sudo docker push "${DOCKER_IMAGE_NAME}:${DOCKER_TAG}"
-	sleep 4 # wait for repo digest
-	@echo git tag --sign --message '$(shell sudo docker image inspect --format '{{join .RepoDigests "\n"}}' "${DOCKER_IMAGE_NAME}:${DOCKER_TAG}")' docker/${DOCKER_TAG} $(shell git rev-parse HEAD)