Bump actions/download-artifact from 3 to 4 in /.github/workflows

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v3...v4)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
...

@dezeroku: align with new download-artifact API

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

.github/workflows/push.yaml

@@ -124,11 +124,14 @@ jobs:
  mkdir -p /tmp/digests
  digest="${{ steps.build.outputs.digest }}"
  touch "/tmp/digests/${digest#sha256:}"
+ PLATFORM=${{ matrix.platform }}
+ # Replace slashes in platform name with dashes
+ echo "PLATFORM_ARTIFACT=${PLATFORM//\//-}" >> $GITHUB_ENV
 
  - name: Upload digest
- uses: actions/upload-artifact@v3
+ uses: actions/upload-artifact@v4
  with:
- name: digests
+ name: digests-${{ env.PLATFORM_ARTIFACT }}
  path: /tmp/digests/*
  if-no-files-found: error
  retention-days: 1
@@ -141,9 +144,10 @@ jobs:
 
  steps:
  - name: Download digests
- uses: actions/download-artifact@v3
+ uses: actions/download-artifact@v4
  with:
- name: digests
+ pattern: digests-*
+ merge-multiple: true
  path: /tmp/digests
 
  - name: Set up Docker Buildx