build(deps): bump docker/metadata-action from 5 to 6 (#1531)

Bumps [docker/metadata-action](https://github.com/docker/metadata-action) from 5 to 6.
- [Release notes](https://github.com/docker/metadata-action/releases)
- [Commits](docker/metadata-action@v5...v6)

---
updated-dependencies:
- dependency-name: docker/metadata-action
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/docker.yml

@@ -34,7 +34,7 @@ jobs:
 
       - name: Set Docker metadata (Ubuntu & NVM variant)
         id: meta-ubuntu
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/${{ github.repository }}/echidna
@@ -126,7 +126,7 @@ jobs:
 
       - name: Set Docker metadata (Ubuntu & NVM variant)
         id: meta-ubuntu
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/${{ github.repository }}/echidna