Bump docker/setup-buildx-action from 2.8.0 to 2.9.1

Bumps [docker/setup-buildx-action](https://github.com/docker/setup-buildx-action) from 2.8.0 to 2.9.1.
- [Release notes](https://github.com/docker/setup-buildx-action/releases)
- [Commits](docker/setup-buildx-action@16c0bc4...4c0219f)

---
updated-dependencies:
- dependency-name: docker/setup-buildx-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/multiarch.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Set up QEMU (to support building on non-native architectures)
         uses: docker/setup-qemu-action@2b82ce82d56a2a04d2637cd93a637ae1b359c0a7
       - name: Set up buildx
-        uses: docker/setup-buildx-action@16c0bc4a6e6ada2cfd8afd41d22d95379cf7c32a
+        uses: docker/setup-buildx-action@4c0219f9ac95b02789c1075625400b2acbff50b1
       - name: Build the multi-arch images
         run: make multiarch-images
       - name: Check that we actually build multi-arch images