chore(ci): migrate to forgejo

.github/workflows/build-docker.yml

@@ -1,19 +0,0 @@
----
-name: Docker
-
-on:
-  push:
-    branches: [ "main" ]
-    tags: [ '*' ]
-  pull_request:
-
-jobs:
-  docker:
-    uses: famedly/github-workflows/.github/workflows/docker.yml@main
-    with:
-      push: ${{ github.event_name != 'pull_request' }} # Always build, don't publish on pull requests
-      registry_user: famedly-ci
-      registry: docker-oss.nexus.famedly.de
-      image_name: openmetrics-vici-exporter
-      build_args: "VERSION=${{ matrix.version }}"
-    secrets: inherit