Clean up github workflows (#233)

.github/workflows/docker.yml

@@ -1,26 +0,0 @@
-name: Build and publish docker image
-
-on:
-  push:
-  pull_request:
-    branches: [ main ]
-
-jobs:
-  build:
-    name: Build and publish docker image
-    runs-on: ubuntu-latest
-    steps:
-      -
-        name: Login to GitHub Container Registry
-        uses: docker/login-action@v2
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-
-      -
-        name: Build and push
-        uses: docker/build-push-action@v3
-        with:
-          push: ${{ github.ref == 'refs/heads/main' }}
-          tags: ghcr.io/matrix-org/matrix-authentication-service:sha-${{ github.sha }}