Bump docker/metadata-action from 3.6.2 to 4.0.1 (alfg#127)

Bumps [docker/metadata-action](https://github.com/docker/metadata-action) from 3.6.2 to 4.0.1.
- [Release notes](https://github.com/docker/metadata-action/releases)
- [Upgrade guide](https://github.com/docker/metadata-action/blob/master/UPGRADE.md)
- [Commits](docker/metadata-action@e562237...69f6fc9)

---
updated-dependencies:
- dependency-name: docker/metadata-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Author: dependabot[bot]

.github/workflows/docker-publish.yml

@@ -20,7 +20,7 @@ jobs:
 
       - name: Extract metadata (tags, labels) for Docker
         id: meta
-        uses: docker/metadata-action@e5622373a38e60fb6d795a4421e56882f2d7a681
+        uses: docker/metadata-action@69f6fc9d46f2f8bf0d5491e4aabe0bb8c6a4678a
         with:
           images: alfg/nginx-rtmp