Revert "add a github action for build multi-arch docker images (#1574)" (#1591)

This reverts commit 2627463366.

## Issue Addressed

This is a temporary fix for #1589, by reverting #1574. The Docker image needs to be built with `--build-arg PORTABLE=true`, and we could probably integrate that into the multi-arch build, but in the interests of expediting a fix, this PR opts for a revert.

.github/workflows/docker.yml

@@ -1,42 +0,0 @@
-name: docker
-
-on:
-    push:
-        branches:
-            - master
-
-jobs:
-    build-docker-image:
-        runs-on: ubuntu-18.04
-        steps:
-            - uses: actions/checkout@master
-
-            - name: Dockerhub login
-              env:
-                  DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}
-                  DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
-              run: |
-                  echo "${DOCKER_PASSWORD}" | docker login --username ${DOCKER_USERNAME} --password-stdin
-
-            - name: Build Docker Buildx
-              run: |
-                  export DOCKER_BUILDKIT=1;
-                  docker build --platform=local -o . git://github.com/docker/buildx;
-                  mkdir -p ~/.docker/cli-plugins;
-                  mv buildx ~/.docker/cli-plugins/docker-buildx;
-
-            - name: Create Docker Builder
-              run: |
-                  docker run --rm --privileged multiarch/qemu-user-static --reset -p yes;
-                  docker context create node-amd64;
-                  docker context create node-arm64;
-                  docker buildx create --use --name lighthouse node-amd64;
-                  docker buildx create --append --name lighthouse node-arm64;
-
-            - name: Build dockerfile (with push)
-              run: |
-                  docker buildx build \
-                      --platform=linux/amd64,linux/arm64 \
-                      --output "type=image,push=true" \
-                      --file ./Dockerfile . \
-                      --tag sigp/lighthouse:latest