chore(deps): update docker/metadata-action action to v6

Author: renovate[bot]

.github/workflows/build-multiarch.yml

@@ -33,7 +33,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Extract Docker metadata
         id: meta
-        uses: docker/metadata-action@c299e40c65443455700f0fdfc63efafe5b349051 # v5.10.0
+        uses: docker/metadata-action@030e881283bb7a6894de51c315a6bfe6a94e05cf # v6
         with:
           images: |
             ghcr.io/jeboehm/fetchmailmgr