Only download .yaml artifacts in promote

The updated docker build-push action is now uploading build results as
GitHub artifacts automatically. These break when download-artifacts is
used in the "download all" style. We could disable those artifacts, but
it's better to be more specific in the download, IMO.

docker/build-push-action#1167

.github/workflows/ci.yml

@@ -180,6 +180,8 @@ jobs:
 
     steps:
       - uses: actions/download-artifact@v4
+        with:
+          pattern: "**/*.yaml"
       - name: Build manifest
         run: |
           cat **/*.yaml > restylers.yaml