release: Always use actions/checkout to ensure we're in a git repo

Otherwise we'll face issues like:
```
Run tag=$(echo $GITHUB_REF | cut -d/ -f3-)
  tag=$(echo $GITHUB_REF | cut -d/ -f3-)
  tarball="kata-static-$tag-amd64.tar.xz"
  mv kata-static.tar.xz "$GITHUB_WORKSPACE/${tarball}"
  pushd $GITHUB_WORKSPACE
  echo "uploading asset '${tarball}' for tag: ${tag}"
  GITHUB_TOKEN=*** gh release upload "${tag}" "${tarball}"
  popd
  shell: /usr/bin/bash -e {0}
~/work/kata-containers/kata-containers ~/work/kata-containers/kata-containers
uploading asset 'kata-static-3.3.0-alpha0-amd64.tar.xz' for tag: 3.3.0-alpha0
failed to run git: fatal: not a git repository (or any of the parent directories): .git
```

Fixes: #8286 (or better, just a follow up of that)

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>
(cherry picked from commit b32c6bf)
Signed-off-by: Greg Kurz <groug@kaod.org>

.github/workflows/release.yaml

@@ -73,6 +73,8 @@ jobs:
     needs: publish-multi-arch-images
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/checkout@v4
+
       - name: download-artifacts-amd64
         uses: actions/download-artifact@v3
         with: