Bump the ci group with 2 updates

Bumps the ci group with 2 updates: [docker/build-push-action](https://github.com/docker/build-push-action) and [sigstore/cosign-installer](https://github.com/sigstore/cosign-installer).


Updates `docker/build-push-action` from 6.5.0 to 6.6.0
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@5176d81...4f7cdeb)

Updates `sigstore/cosign-installer` from 3.5.0 to 3.6.0
- [Release notes](https://github.com/sigstore/cosign-installer/releases)
- [Commits](sigstore/cosign-installer@59acb62...4959ce0)

---
updated-dependencies:
- dependency-name: docker/build-push-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: ci
- dependency-name: sigstore/cosign-installer
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: ci
...

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

Author: dependabot[bot]

.github/workflows/nightly.yaml

@@ -22,7 +22,7 @@ jobs:
         id: buildx
         uses: docker/setup-buildx-action@988b5a0280414f521da01fcc63a27aeeb4b104db # v3.6.1
       - name: Build multi-arch container image
-        uses: docker/build-push-action@5176d81f87c23d6fc96624dfdbcd9f3830bbe445 # v6.5.0
+        uses: docker/build-push-action@4f7cdeb0f05278b464e71357394bf2c61f94138e # v6.6.0
         with:
           push: false
           builder: ${{ steps.buildx.outputs.name }}

.github/workflows/release.yml

@@ -68,7 +68,7 @@ jobs:
             type=raw,value=${{ steps.prep.outputs.VERSION }}
       - name: Publish images
         id: build-push
-        uses: docker/build-push-action@5176d81f87c23d6fc96624dfdbcd9f3830bbe445 # v6.5.0
+        uses: docker/build-push-action@4f7cdeb0f05278b464e71357394bf2c61f94138e # v6.6.0
         with:
           sbom: true
           provenance: true
@@ -79,7 +79,7 @@ jobs:
           platforms: linux/amd64,linux/arm/v7,linux/arm64
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-      - uses: sigstore/cosign-installer@59acb6260d9c0ba8f4a2f9d9b48431a222b68e20 # v3.5.0
+      - uses: sigstore/cosign-installer@4959ce089c160fddf62f7b42464195ba1a56d382 # v3.6.0
       - name: Sign images
         env:
           COSIGN_EXPERIMENTAL: 1