Bump actions/attest-build-provenance from 1 to 2

Bumps [actions/attest-build-provenance](https://github.com/actions/attest-build-provenance) from 1 to 2.
- [Release notes](https://github.com/actions/attest-build-provenance/releases)
- [Changelog](https://github.com/actions/attest-build-provenance/blob/main/RELEASE.md)
- [Commits](actions/attest-build-provenance@v1...v2)

---
updated-dependencies:
- dependency-name: actions/attest-build-provenance
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/docker.yml

@@ -85,7 +85,7 @@ jobs:
       # TODO: enable push to registry when referrers API will be supported by ghcr.io
       - name: Attest Build Provenance
         if: github.event_name != 'pull_request'
-        uses: actions/attest-build-provenance@v1
+        uses: actions/attest-build-provenance@v2
         with:
           subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           subject-digest: ${{ steps.build-and-push.outputs.digest }}