.github: delete metropolis release workflow

The workflow would need to be updated to push the new node OS image OCI
artifacts to a registry. But the gha-trusted runner no longer exists, so
there is no way to test changes and the workflow doesn't work anyway.

Change-Id: I2f0cab823007dceeac111e37cc37f44f0a2c0948
Reviewed-on: https://review.monogon.dev/c/monogon/+/4094
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/.github/workflows/release-metropolis.yml b/.github/workflows/release-metropolis.yml
deleted file mode 100644
index ed423bf..0000000
--- a/.github/workflows/release-metropolis.yml
+++ /dev/null
@@ -1,37 +0,0 @@
-name: Publish release artifacts and docs for new tags
-on:
-  push:
-    tags:
-      - "metropolis-v*"
-jobs:
-  publish:
-    runs-on: gha-trusted
-    permissions:
-      contents: "write" # Required for publishing release artifacts
-      id-token: "write"
-    steps:
-      - uses: actions/checkout@v3
-      - id: auth
-        name: Authenticate to GCP
-        uses: google-github-actions/auth@v0.8.0
-        with:
-          create_credentials_file: "true"
-          workload_identity_provider: "projects/498345658902/locations/global/workloadIdentityPools/oidc-fed/providers/github-actions"
-          service_account: "github-artifact-deploy@monogon-infra.iam.gserviceaccount.com"
-      - name: Set up Cloud SDK
-        uses: google-github-actions/setup-gcloud@v0
-      - name: Install Cloud SDK alpha commands
-        run: gcloud --quiet components install alpha
-      - name: Build artifacts
-        run: bazel build -c opt //metropolis/node:bundle //metropolis/handbook //metropolis/cli/metroctl
-      - name: Attach artifacts to Release
-        uses: softprops/action-gh-release@v1
-        with:
-          files: |
-            bazel-bin/metropolis/node/bundle.zip
-            bazel-bin/metropolis/cli/metroctl/metroctl_/metroctl
-      - name: Upload to GCS
-        run: |-
-          gcloud alpha storage cp bazel-bin/metropolis/node/bundle.zip gs://monogon-release-artifacts/${GITHUB_REF##*/}/bundle.zip
-          gcloud alpha storage cp bazel-bin/metropolis/cli/metroctl/metroctl_/metroctl gs://monogon-release-artifacts/${GITHUB_REF##*/}/metroctl
-          gcloud alpha storage cp -r bazel-bin/metropolis/handbook/handbook gs://monogon-release-artifacts/${GITHUB_REF##*/}/handbook