CI(deps): Update docker/metadata-action action to v6 (releasebranch_8_5) (#7168)

Author: renovate[bot]

.github/workflows/docker.yml

@@ -141,7 +141,7 @@ jobs:
           echo "current is ${current}"
       - name: Docker meta
         id: meta
-        uses: docker/metadata-action@c299e40c65443455700f0fdfc63efafe5b349051 # v5.10.0
+        uses: docker/metadata-action@030e881283bb7a6894de51c315a6bfe6a94e05cf # v6.0.0
         with:
           images: |
             name=docker.io/osgeo/grass-gis,enable=${{ github.repository_owner == 'OSGeo'