chore(deps): update quay.io/skopeo/stable docker tag to v1.20.0

Author: renovate[bot]

.github/actions/copy-images/action.yml

@@ -29,7 +29,7 @@ runs:
       shell: bash
       env:
         # renovate: datasource=docker depName=quay.io/skopeo/stable versioning=loose
-        SKOPEO_VERSION: "v1.20.0-immutable"
+        SKOPEO_VERSION: "v1.20.0"
         SUFFIX: ${{ inputs.test_registry_suffix }}
       run: |
         images=$(echo '${{ inputs.bake_build_metadata }}' |