chore(deps): update docker/bake-action action to v6 (#20)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Tommaso Bailetti <tommaso.bailetti@nethesis.it>

Author: renovate[bot]

.github/workflows/build.yml

@@ -46,13 +46,13 @@ jobs:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ github.token }}
-      - uses: docker/bake-action@v5
+      - uses: docker/bake-action@v6
         with:
           targets: production
           files: |
             ./docker-bake.hcl
-            ${{ steps.meta-php.outputs.bake-file }}
-            ${{ steps.meta-nginx.outputs.bake-file }}
+            cwd://${{ steps.meta-php.outputs.bake-file }}
+            cwd://${{ steps.meta-nginx.outputs.bake-file }}
           sbom: true
           provenance: true
           push: true